JP2008041779A - Solid-state image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state image pickup device comprising a color filter having a light transmission rate higher than ever before. <P>SOLUTION: The solid-state image pickup device comprises a semiconductor substrate 101 having photoelectric converters 103R, 103G, and 103B; a dielectric film 104 arranged on the semiconductor substrate 101; and a semiconductor film 105 arranged on the dielectric film 104. Regions 104R, 104G, and 104B of the dielectric film 104 which correspond to the respective photoelectric converters have film thicknesses, 200 nm, 170 nm, and 140 nm, according to the wavelength regions (center wavelengths 610 nm, 530 nm, and 450 nm) of light to be incident on respective photoelectric conversion portions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device used for a digital camera or the like, and more particularly to improvement of a color filter.

In solid-state imaging devices, color filters using organic materials are widely used (for example, see Patent Documents 1 and 2). Recently, color filters using inorganic materials have been proposed from the viewpoint of light resistance and heat resistance. (For example, see Patent Document 3).
Patent Document 3 discloses a technique using a single layer film made of amorphous silicon as a color filter. In Patent Document 3, by setting the film thickness of amorphous silicon to about half the wavelength of light, light in a wavelength region corresponding to the film thickness is transmitted using the interference effect of light. Thus, by using amorphous silicon for the color filter, light resistance and heat resistance can be improved. Further, since a single layer film is used for the color filter, the number of manufacturing steps can be reduced as compared with the case of using a multilayer film.
Japanese Patent Laid-Open No. 5-6986 JP 7-311310 A WO2006 / 028128

In recent years, with the miniaturization of pixels, the amount of incident light per pixel has been decreasing more and more. Therefore, it is desirable to reduce the loss of incident light as much as possible by using a color filter having a high light transmittance. However, the color filter according to Patent Document 3 has a problem that light transmittance is relatively low because the light absorption coefficient of amorphous silicon is relatively large.
Accordingly, an object of the present invention is to provide a solid-state imaging device including a color filter having a higher light transmittance than the conventional one.

  A solid-state imaging device according to the present invention includes a semiconductor substrate having a plurality of photoelectric conversion units, a dielectric film disposed on the semiconductor substrate, and a semiconductor film disposed on the dielectric film, Each area | region corresponding to each photoelectric conversion part in a body film has a film thickness according to the wavelength range of the light which should enter into a corresponding photoelectric conversion part, respectively.

  According to the above configuration, the color filter function is realized by the occurrence of light interference in the dielectric film sandwiched between the semiconductor substrate and the semiconductor film. In general, the light absorption coefficient of a dielectric is extremely small compared to the light absorption coefficient of amorphous silicon. Therefore, by causing light interference in the dielectric film, light absorption can be suppressed more than before, and as a result, the light transmittance can be increased.

In addition, each region corresponding to each photoelectric conversion unit in the dielectric film has a center wavelength of a wavelength range of light to be incident on the corresponding photoelectric conversion unit, λ, and a refractive index of a material constituting the dielectric film. When it is set to n, it is good also as having the film thickness calculated by (lambda) / (2n).
According to the above configuration, a predetermined film thickness can be easily designed.
Moreover, each area | region corresponding to each photoelectric conversion part in the said dielectric film is good also as having the film thickness in any one of several types of film thickness, respectively.

According to the above configuration, light in any one of a plurality of wavelength ranges of light is incident on each photoelectric conversion unit. Therefore, a color image can be obtained based on the signal generated by each photoelectric conversion unit.
The dielectric film includes an adjacent layer adjacent to the semiconductor substrate and a non-adjacent layer disposed on the adjacent layer, and each region corresponding to each photoelectric conversion unit in the adjacent layer is the same. The regions corresponding to the photoelectric conversion portions in the non-adjacent layer have different layer thicknesses, and the etching rate of the material constituting the adjacent layer is the material constituting the semiconductor substrate. It is good also as lower than both of the etching rate of this, and the etching rate of the material which comprises the said nonadjacent layer.

According to the above configuration, the adjacent layer can function as an etching stopper. Therefore, the controllability of the layer thickness can be improved when the layer thickness of the non-adjacent layer is varied for each region by using etching.
Further, the adjacent layer serves as a protective film, and damage to the semiconductor substrate due to etching can be reduced during processing of the non-adjacent layer.

The adjacent layer may be made of silicon nitride or silicon oxynitride, and the non-adjacent layer may be made of silicon dioxide.
According to the above configuration, the dielectric film can be formed using a semiconductor process. Therefore, the dielectric film can be easily formed.
Moreover, each area | region corresponding to each photoelectric conversion part in the said semiconductor film is good also as all having the same film thickness.

According to the above configuration, the semiconductor film can be formed by depositing the material constituting the semiconductor film over the entire area of the dielectric film. Therefore, the semiconductor film can be easily formed.
The semiconductor film may be made of amorphous silicon, polysilicon, single crystal silicon, or a material containing silicon as a main component.

Each of these materials has a refractive index of about 5, which is extremely large as compared with a general dielectric material. Therefore, the reflectance at the interface between the semiconductor film and the dielectric film is high, and the light interference effect can be enhanced.
The semiconductor film may have a thickness of 100 nm or less.
According to the above configuration, light absorption in the semiconductor film can be reduced. Accordingly, the sensitivity of the solid-state imaging device can be improved.

The solid-state imaging device may further include an antireflection film disposed on the semiconductor film.
According to the above configuration, reflection of incident light can be prevented. Accordingly, the sensitivity of the solid-state imaging device can be improved.
The anti-prevention film may be made of silicon nitride or silicon oxynitride.

According to the above configuration, the dielectric film can be formed using a semiconductor process. Therefore, the dielectric film can be easily formed.
The silicon nitride or silicon oxynitride may be formed by using low pressure CVD.
According to the above configuration, the density of silicon nitride or silicon oxynitride can be increased. Therefore, these can function as a protective film.

A solid-state imaging device according to the present invention includes a semiconductor substrate having a plurality of photoelectric conversion units, a dielectric film disposed on the semiconductor substrate, and a semiconductor film disposed on the dielectric film, Each area | region corresponding to each photoelectric conversion part in a body film has either film thickness in multiple types, respectively.
According to the above configuration, the color filter function is realized by the occurrence of light interference in the dielectric film sandwiched between the semiconductor substrate and the semiconductor film. In general, the light absorption coefficient of a dielectric is extremely small compared to the light absorption coefficient of amorphous silicon. Therefore, by causing light interference in the dielectric film, light absorption can be suppressed more than before, and as a result, the light transmittance can be increased. Moreover, according to the said structure, the light of any wavelength range in the wavelength range of multiple types of light injects into each photoelectric conversion part. Therefore, a color image can be obtained based on the signal generated by each photoelectric conversion unit.

The best mode for carrying out the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a diagram showing a schematic configuration of a solid-state imaging device according to the present invention.
The solid-state imaging device 1 includes a pixel 2, a vertical shift register 3, a horizontal shift register 4, and a drive circuit 5. The pixels 2 are two-dimensionally arranged, and only the pixels selected by the vertical shift register 3 and the horizontal shift register 4 output pixel signals. The vertical shift register 3 and the horizontal shift register 4 are driven by a drive circuit 5.

FIG. 2 is a schematic cross-sectional view of the solid-state imaging device according to Embodiment 1 of the present invention.
The solid-state imaging device 1 includes a semiconductor substrate 101, a dielectric film 104, and a semiconductor film 105 as main components. On the semiconductor film 105, an interlayer insulating film 106, a light shielding film 107, and a microlens 108 are disposed.
The semiconductor substrate 101 includes a well 102, and photoelectric conversion units 103R, 103G, and 103B are included in the well 102.

The dielectric film 104 is made of silicon dioxide, and has different thicknesses for the regions 104R, 104G, and 104B corresponding to the photoelectric conversion units 103R, 103G, and 103B, respectively. Specifically, the thicknesses of the regions 104R, 104G, and 104B are 200 nm, 170 nm, and 140 nm, respectively.
The semiconductor film 105 is made of amorphous silicon and has the same film thickness in any of the regions corresponding to the photoelectric conversion units 103R, 103G, and 103B. Specifically, the thickness of the semiconductor film 105 is 30 nm.

  According to such a configuration, the color filter function is realized by the occurrence of light interference in the dielectric film 104 sandwiched between the semiconductor substrate 101 and the semiconductor film 105. Since light interference is used, the relationship between the center wavelength λ of the light transmission wavelength region, the refractive index n of the material constituting the dielectric film 104, and the film thickness d of the dielectric film 104 is nd = λ / 2. Satisfy the formula. Accordingly, when it is desired to set the center wavelength λ to 610 nm, 530 nm, and 450 nm, since the refractive index of silicon dioxide is 1.47, 1.50, and 1.55 at each wavelength, the films in the regions 104R, 104G, and 104B The thicknesses are 200 nm, 170 nm, and 140 nm, respectively.

FIG. 3 is a diagram showing the transmission characteristics of the color filter according to Embodiment 1 of the present invention.
The transmittance shown here is derived by the matrix method using the Fresnel coefficient. The transmittance curves 10R, 10G, and 10B are the transmittances of the region 104R corresponding to the photoelectric conversion unit 103R, the region 104G corresponding to the photoelectric conversion unit 103G, and the region 104B corresponding to the photoelectric conversion unit 103B in the dielectric film 104, respectively. Represents. According to this, the regions 104R, 104G, and 104B of the dielectric film 104 have wavelengths centered at about 610 nm (see the curve 10R), about 530 nm (see the curve 10G), and about 450 nm (see the curve 10B), respectively. Transmits light in the area. Note that the transmittance peaks of the regions 104R, 104G, and 104B in the dielectric film 104 are relatively high values of about 80%, about 70%, and about 60%, respectively. This is because the light absorption coefficient of silicon dioxide is extremely small, and light absorption is suppressed.

FIG. 4 is a diagram showing a manufacturing process of the color filter according to Embodiment 1 of the present invention.
First, a layer 104a is formed by depositing silicon dioxide on a semiconductor substrate 101 (FIG. 4 shows a well 102 and photoelectric conversion portions 103R, 103G, and 103B) by using a CVD (Chemical Vapor Deposition) method. Laminate (FIG. 4A). The thickness of the layer 104a is 30 nm.

Next, the remaining region of the layer 104a is covered with a mask 110 (FIG. 4B), and dry etching is performed to remove unnecessary regions (FIG. 4C).
Next, after peeling off the mask 110 (FIG. 4D), a layer 104b is deposited on the semiconductor substrate 101 by depositing silicon dioxide using a CVD method (FIG. 4E). The thickness of the layer 104b is 30 nm.

Next, the remaining region of the layer 104b is covered with a mask 111 (FIG. 4F), and dry etching is performed to remove unnecessary regions (FIG. 4G).
Next, after peeling off the mask 111 (FIG. 4H), a layer 104c is deposited on the semiconductor substrate 101 by depositing silicon dioxide using the CVD method (FIG. 4I). The thickness of the layer 104c is 140 nm.

Next, the semiconductor film 105 is formed by depositing amorphous silicon on the semiconductor substrate 101 (FIG. 4J). The thickness of the semiconductor film 105 is 30 nm.
The layers 104 a, 104 b, and 104 c thus formed become the dielectric film 104.
(Embodiment 2)
FIG. 5 is a schematic cross-sectional view of the solid-state imaging device according to Embodiment 2 of the present invention.

The second embodiment is different from the first embodiment in that an antireflection film 209 is disposed on the semiconductor layer 205. Since the other points are the same as in the first embodiment, the description thereof is omitted.
The antireflection film 209 is made of silicon nitride, and has the same film thickness in any of the regions corresponding to the photoelectric conversion units 103R, 103G, and 103B. Specifically, the film thickness of the antireflection film 209 is 50 nm.

The interlayer insulating film 206 is made of silicon dioxide.
In general, when light is incident on the medium B from the medium A, the reflectivity R at the boundary surface between the medium A and the medium B is expressed as R = (if the refractive index of the medium A is na and the refractive index of the medium B is nb. (na-nb) / (na + nb)) ² is satisfied.
If the reflectance of light passing through the interlayer insulating film 206, the antireflection film 209, and the semiconductor film 205 is evaluated using this relational expression, it can be seen that light reflection can be reduced as compared with the case where the antireflection film 209 is not present. . Here, the refractive indexes of silicon dioxide, silicon nitride, and amorphous silicon are 1.55, 2.00, and 4.77, respectively. Thus, by providing the antireflection film 209, the light transmittance can be increased.

FIG. 6 is a diagram showing the transmission characteristics of the color filter according to Embodiment 2 of the present invention.
The transmittance curves 20R, 20G, and 20B respectively indicate the transmittance of the region 204R corresponding to the photoelectric conversion unit 203R, the region 204G corresponding to the photoelectric conversion unit 203G, and the region 204B corresponding to the photoelectric conversion unit 203B in the dielectric film 204. Represents. According to this, the transmittance peaks of the regions 204R, 204G, and 204B in the dielectric film 204 are about 90%, about 85%, and about 65%, which are higher than those in the first embodiment. This is an effect obtained by providing the antireflection film 209.
(Embodiment 3)
FIG. 7 is a schematic cross-sectional view of a solid-state imaging device according to Embodiment 3 of the present invention.

The third embodiment is different from the first embodiment in that the dielectric film 304 is composed of two layers. Since the other points are the same as in the first embodiment, the description thereof is omitted.
The dielectric film 304 includes layers 304u and 304v.
The layer 304u is made of silicon nitride and has the same film thickness in any of the regions 304uR, 304uG, and 304uB corresponding to the photoelectric conversion portions 303R, 303G, and 303B, respectively. Specifically, the thickness of each region 304uR, 304uG, 304uB of the layer 304u is 50 nm.

The layer 304v is made of silicon dioxide, and has a different thickness for each of the regions 304vR, 304vG, and 304vB corresponding to the photoelectric conversion units 303R, 303G, and 303B. Specifically, the thicknesses of the regions 304vR, 304vG, and 304vB are 140 nm, 100 nm, and 70 nm, respectively.
The film thickness of each region 304R, 304G, 304B of the dielectric film 304 is designed so that the two layers together satisfy the relational expression nd = λ / 2.

According to such a configuration, the layer 304u can function as an etching stopper by appropriately selecting an etching gas. Therefore, the controllability of the layer thickness can be improved when etching is used to vary the layer thickness of the layer 304v for each region. Here, for example, C ₅ F ₈ + O ₂ or C ₄ F ₆ + O ₂ can be used as the etching gas. If these are employed as the etching gas, the selection ratio of silicon nitride to silicon dioxide is about 1:20, so that silicon nitride functions sufficiently as an etching stopper. Further, silicon nitride serves as a protective film, and damage to the semiconductor substrate 301 due to etching during the processing of the layer 304v can be reduced.

  Note that silicon nitride is more preferably deposited using the LPCVD (Low Pressure CVD) method than the PECVE (Plasma Enhanced CVD) method. This is because use of the LPCVD method can increase the density of the layer 304u and is preferable from the viewpoint of causing the layer 304u to function as a protective film. Although silicon nitride is taken as an example here, silicon oxynitride may be used.

FIG. 8 is a diagram showing the transmission characteristics of the color filter according to Embodiment 3 of the present invention.
The transmittance curves 30R, 30G, and 30B respectively indicate the transmittance of the region 304R corresponding to the photoelectric conversion unit 303R, the region 304G corresponding to the photoelectric conversion unit 303G, and the region 304B corresponding to the photoelectric conversion unit 303B of the dielectric film 304. Represents. According to this, the transmittance peaks of the regions 304R, 304G, and 304B in the dielectric film 304 indicate about 75%, about 60%, and about 55%, respectively.
(Embodiment 4)
FIG. 9 is a schematic cross-sectional view of a solid-state imaging device according to Embodiment 4 of the present invention.

The fourth embodiment is different from the third embodiment in that the layer 404vB corresponding to the photoelectric conversion unit 403B in the layer 404v has a layer thickness of 0 nm. Since the other points are the same as those of the third embodiment, description thereof is omitted.
The dielectric film 404 includes layers 404u and 404v.
The layer 404u is made of silicon nitride, and has the same film thickness in any of the regions 404uR, 404uG, and 404uB corresponding to the photoelectric conversion units 403R, 403G, and 403B. Specifically, the thickness of each region 404uR, 404uG, 404uB of the layer 404u is 100 nm.

The layer 404v is made of silicon dioxide, and has different film thicknesses for the regions 404vR, 404vG, and 404vB corresponding to the photoelectric conversion units 403R, 403G, and 403B, respectively. Specifically, the thicknesses of the regions 404vR, 404vG, and 404vB are 40 nm, 20 nm, and 0 nm, respectively.
The film thicknesses of the respective regions 404R, 404G, and 404B of the dielectric film 404 are designed so as to satisfy the relational expression of nd = λ / 2 when the two layers are combined.

FIG. 10 is a diagram showing the transmission characteristics of the color filter according to Embodiment 4 of the present invention.
The transmittance curves 40R, 40G, and 40B respectively indicate the transmittance of the region 404R corresponding to the photoelectric conversion unit 403R, the region 404G corresponding to the photoelectric conversion unit 403G, and the region 404B corresponding to the photoelectric conversion unit 403B of the dielectric film 404. Represents. According to this, the transmittance peaks of the regions 404R, 404G, and 404B of the dielectric film 404 are about 75%, about 70%, and about 65%, respectively.

FIG. 11 is a diagram illustrating a manufacturing process of the color filter according to the fourth embodiment of the present invention.
First, on the semiconductor substrate 401 (in FIG. 11, the well 402 and the photoelectric conversion units 403R, 403G, and 403B are shown), a layer 404u is stacked by depositing silicon nitride using the LPCVD method. A layer 404a is deposited on the layer 404u by depositing silicon dioxide using the CVD method (FIG. 11A). The thickness of the layer 404a is 20 nm.

Next, the remaining area of the layer 404a is covered with a mask 410 (FIG. 11B), and dry etching is performed to remove unnecessary areas (FIG. 11C).
Next, after peeling the mask 410 (FIG. 11D), a layer 404b is deposited on the semiconductor substrate 401 by depositing silicon dioxide using a CVD method (FIG. 11E). The thickness of the layer 404b is 20 nm.

Next, the remaining region of the layer 404b is covered with a mask 411 (FIG. 11F), and dry etching is performed to remove unnecessary regions (FIG. 11G).
Next, after the mask 411 is peeled off (FIG. 11H), a semiconductor film 405 is formed by depositing amorphous silicon on the semiconductor substrate 401 (FIG. 11I). The thickness of the semiconductor film 405 is 30 nm.

The layers 404a and 404b become the layer 404v. Thus, the number of manufacturing steps can be reduced by setting the layer thickness of the region 404vB to 0 nm.
Although the solid-state imaging device according to the present invention has been described based on the embodiments, the present invention is not limited to these embodiments. For example, the following modifications can be considered.
(1) In the embodiment, the types of film thickness of the dielectric film are three types (R, G, B), but the present invention is not limited to this. For example, one type, two types, or four or more types may be used.
(2) In the embodiment, the thickness of the dielectric film is set so that the center wavelength of the transmission wavelength region is 610 nm, 530 nm, and 450 nm, but the present invention is not limited to this. For example, the center wavelength of the transmission wavelength region may be an infrared region or an ultraviolet region.
(3) In the embodiment, silicon dioxide and silicon nitride are cited as materials constituting the dielectric film, but the present invention is not limited to this. As a material constituting the dielectric film, for example, titanium dioxide (TiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), zirconium oxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ), hafnium oxide (HfO ₃ ), Magnesium oxide (MgO ₂ ), magnesium fluoride (MgF ₂ ), or the like may be employed.

  The present invention can be applied to a digital camera.

It is a figure which shows schematic structure of the solid-state imaging device concerning this invention. 1 is a schematic cross-sectional view of a solid-state imaging device according to Embodiment 1 of the present invention. It is a figure which shows the permeation | transmission characteristic of the color filter which concerns on Embodiment 1 of this invention. It is a figure which shows the manufacturing process of the color filter which concerns on Embodiment 1 of this invention. It is a cross-sectional schematic diagram of the solid-state imaging device which concerns on Embodiment 2 of this invention. It is a figure which shows the permeation | transmission characteristic of the color filter which concerns on Embodiment 2 of this invention. It is a cross-sectional schematic diagram of the solid-state imaging device which concerns on Embodiment 3 of this invention. It is a figure which shows the permeation | transmission characteristic of the color filter which concerns on Embodiment 3 of this invention. It is a cross-sectional schematic diagram of the solid-state imaging device which concerns on Embodiment 4 of this invention. It is a figure which shows the permeation | transmission characteristic of the color filter which concerns on Embodiment 4 of this invention. It is a figure which shows the manufacture process of the color filter which concerns on Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solid-state imaging device 2 Pixel 3 Vertical shift register 4 Horizontal shift register 5 Drive circuit 101, 201, 301, 401 Semiconductor substrate 102, 202, 302, 402 Well 103, 203, 303, 403 Photoelectric conversion part 104, 204, 304, 404 Dielectric film 105, 205, 305, 405 Semiconductor film 106, 206, 306, 406 Interlayer insulating film 107, 207, 307, 407 Light shielding film 108, 208, 308, 408 Micro lens 110, 111, 410, 411 Mask 209 Anti-reflection coating

Claims (12)

A semiconductor substrate having a plurality of photoelectric conversion parts;
A dielectric film disposed on the semiconductor substrate;
A semiconductor film disposed on the dielectric film,
Each area | region corresponding to each photoelectric conversion part in the said dielectric material film has a film thickness according to the wavelength range of the light which should be incident on a corresponding photoelectric conversion part, respectively. The solid-state imaging device characterized by the above-mentioned. Each region corresponding to each photoelectric conversion unit in the dielectric film has a center wavelength of a wavelength region of light to be incident on the corresponding photoelectric conversion unit as λ, and a refractive index of a material constituting the dielectric film as n. The solid-state imaging device according to claim 1, wherein the solid-state imaging device has a film thickness calculated by λ / (2n). 2. The solid-state imaging device according to claim 1, wherein each region of the dielectric film corresponding to each photoelectric conversion unit has any one of a plurality of types of film thicknesses. The dielectric film is composed of an adjacent layer adjacent to the semiconductor substrate and a non-adjacent layer disposed on the adjacent layer,
Each region corresponding to each photoelectric conversion portion in the adjacent layer has the same layer thickness,
Each region corresponding to each photoelectric conversion portion in the non-adjacent layer has a different layer thickness,
The etching rate of the material constituting the adjacent layer is smaller than both the etching rate of the material constituting the semiconductor substrate and the etching rate of the material constituting the non-adjacent layer. Solid-state imaging device. The adjacent layer is made of silicon nitride or silicon oxynitride,
The solid-state imaging device according to claim 4, wherein the non-adjacent layer is made of silicon dioxide. 2. The solid-state imaging device according to claim 1, wherein each region corresponding to each photoelectric conversion unit in the semiconductor film has the same film thickness. The solid-state imaging device according to claim 1, wherein the semiconductor film is made of amorphous silicon, polysilicon, single crystal silicon, or a material containing silicon as a main component. The solid-state imaging device according to claim 1, wherein the semiconductor film has a thickness of 100 nm or less. The solid-state imaging device further includes:
The solid-state imaging device according to claim 1, further comprising an antireflection film disposed on the semiconductor film. The solid-state imaging device according to claim 9, wherein the antireflection film is made of silicon nitride or silicon oxynitride. The solid-state imaging device according to claim 5 or 10, wherein the silicon nitride or silicon oxynitride is formed by using low pressure CVD. A semiconductor substrate having a plurality of photoelectric conversion parts;
A dielectric film disposed on the semiconductor substrate;
A semiconductor film disposed on the dielectric film,
Each area | region corresponding to each photoelectric conversion part in the said dielectric material film has either one of several types of film thickness, respectively. The solid-state imaging device characterized by the above-mentioned.

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