JP2003209231A - Solid-state imaging device and system thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging device which can shorten a distance between a microlens and a light receiving surface and can design the thickness of an anti-reflection film easily and optimumly and produce less cracking when the film is formed. <P>SOLUTION: The solid-state imaging device at least having a light receiving part 109 and a microlens is arranged so that the surface of the microlens comes into contact with a vapor phase. A refractive-index distribution region 103(a) having a refractive index spread as varied is formed as associated with the light receiving part 109 in a planarized layer 103 provided on an incident light side of the light receiving part 109 to thereby form a microlens. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device and a solid-state image pickup system in which incident light is condensed on a light receiving portion by a microlens.

[0002]

2. Description of the Related Art In recent years, solid-state image pickup devices have been developed to reduce the size of light-receiving chips and increase the number of pixels because of the demand for higher image resolution and smaller image pickup systems.

In order to achieve the miniaturization of the chip and the increase in the number of pixels, it is essential to reduce the pixel size. In order to compensate for the decrease in the electrical output signal due to the reduction of the light receiving area, measures such as increasing the sensitivity of the photoelectric conversion element, improving the S / N ratio, and substantially increasing the aperture ratio of each pixel are taken.

The microlens is designed for the purpose of improving the utilization efficiency of the light incident on the chip, and effectively condenses the light rays incident on a predetermined pixel region on the light receiving region to substantially open the aperture. I'm raising the rate.

The microlens is usually provided corresponding to each light receiving portion. As a method for forming the microlens, a method using a photolithography method is generally used. In this method, after the upper surface of the opening is flattened with a transparent resin, a photosensitive resin to be a microlens is formed into an island shape by photolithography so as to correspond to each light receiving portion, and the island resin is heated. Is softened, and the surface tension makes the surface spherical to form a curved microlens.

[0006]

However, the microlens formed as described above has a color filter and a flattening layer formed on the light receiving portion and must be formed on the color filter and the flattening layer. It is difficult to shorten the distance to the part, which has been a major limitation in raising the numerical aperture of the microlens.

Further, in the microlens formed as described above, the interface of the microlens resin having a high refractive index is exposed, so that the reflection loss of incident light is large, the light utilization efficiency for image formation is lowered, and the stray light is lost. The increase in the components causes a reduction in contrast and a reduction in image quality such as a ghost.

When an antireflection film such as an inorganic thin film is formed on the surface of the microlens made of an organic resin material in order to reduce the reflection loss on the surface of the microlens,
Another problem is that cracks easily form on the surface due to the difference in their thermal properties. In the case of an image sensor array in which each of them must perform an equivalent imaging function,
The occurrence of cracks is fatal, and it has been desired to prevent the occurrence of cracks.

Further, when designing the film thickness of the antireflection film, the angular dependence of the incident light on the surface of the microlens and the distribution of the film thickness which is inevitably generated when the antireflection film is formed are taken into consideration. However, it is also difficult to design the optimum film thickness.

The present invention has been made in view of the above points, and it is possible to shorten the distance between the microlens and the light receiving portion, and at the same time, to easily design the optimum film thickness when the antireflection film is formed. An object of the present invention is to provide a solid-state imaging device and a solid-state imaging system in which cracks are unlikely to occur.

[0011]

In order to solve the above problems, a solid-state image pickup device according to the present invention has at least a light receiving portion and a microlens, and the surface of the microlens is in contact with a gas phase. In the solid-state imaging device configured as described above, in the flattening layer provided on the light incident side of the light receiving unit, the microlenses are formed by forming a refractive index distribution in which the refractive index spreads and changes corresponding to the light receiving unit. It is characterized by being formed.

A solid-state image pickup device according to the present invention includes a light receiving portion,
In a solid-state imaging device having at least a flattening layer provided on the light receiving portion and a microlens, and configured so that the surface of the microlens is in contact with the gas phase, the flattening layer has a refractive index spreading. It is characterized in that the microlens is formed by forming a refractive index distribution that changes as a result.

A solid-state image pickup device according to the present invention includes a light receiving section,
In a solid-state imaging device having at least a color filter provided on the light-receiving unit and a microlens, and the surface of the microlens being in contact with the gas phase, the refractive index of the color filter changes and spreads. The microlens is formed by forming a refractive index distribution that

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic sectional view of the first embodiment. In FIG. 1, 110 is an antireflection film, 1
Reference numeral 02 represents the surface of the surface flattening layer 103, and 103 represents the surface flattening layer. The surface flattening layer 103 is formed on the light incident side of the light receiving portion (photoelectric conversion element) 109 and is made of a low refractive index resin. A refractive index distribution region 103a is formed on the surface flattening layer 103 so as to correspond to the light receiving portion 109. 103b is a low refractive index resin region. The refractive index distribution region 103a has a structure in which the refractive index gradually decreases while expanding from the upper side to the lower side of the surface flattening layer 103. The curve in FIG. 1 shows the situation.

The refractive index distribution region 103a functions as a microlens and collects incident light in the light receiving portion. Although FIG. 1 illustrates that each area has a boundary, in reality, these areas do not have a clear boundary. Further, the refractive index distribution region 103a is formed on the surface flattening layer 10
Since it is formed inside 3, the surface is substantially flat.

Further, 104 is a color filter and 105
Is an in-layer flattening layer, 106 is a light-shielding film, 107 is an interlayer insulating layer, 108 is a wiring, and 109 is a light receiving portion.

The manufacturing method of this embodiment will be described below. First, the light receiving portion 1 is formed on a wafer made of silicon or the like.
09, wiring 108, interlayer insulating layer 107, light shielding layer 106,
The in-layer planarization layer 105 is formed. Since this method is performed in the conventional semiconductor manufacturing process, its description is omitted. Then, the color filter 104 is formed. Since this method is also performed in the conventional color filter forming step, its explanation is omitted.

After forming the color filter 104, a surface flattening layer 103 made of a low refractive index resin such as an acrylic resin is formed in order to flatten the irregularities of the color filter 104. Then, a refractive index distribution region is formed at a desired position on the surface of the surface flattening layer 103 by the diffusion polymerization method disclosed in JP-A 06-94903. The surface flatness in the refractive index distribution region is 0.2 within one region.
Within μm.

Next, an antireflection film 110 is formed on the surface 102 of the surface flattening layer. As the forming method, a general method for forming an antireflection film can be used. The antireflection film 110 of the present embodiment is formed of a four-layer laminated film of titanium oxide / silicon oxide and has a reflectance of 2% or less in the visible region of 400 to 700 nm.

In this embodiment, the diffusion polymerization method is used as the method of forming the gradient index region, but other than that, the ion exchange method disclosed in JP-A-61-251540 and JP-A-02-310501 are used. There is a selective polymerization method and the like disclosed in the publication. This forming method can be selected and applied according to the design of the function of the microlens in the refractive index distribution region.

(Embodiment 2) This embodiment is the same as Embodiment 1.
However, the material of the antireflection film 110 and the method of forming the same are different. In the present embodiment, the antireflection film 1
CYTOP (made by Asahi Glass) containing a low refractive index fluororesin as an organic material is used as 10, and a dipping method is used as a forming method.

The manufacturing method of this embodiment will be described below. First, the light receiving portion 1 is formed on a wafer made of silicon or the like.
09, wiring 108, interlayer insulating layer 107, light shielding layer 106,
The in-layer planarization layer 105 is formed. Since this method is performed in the conventional semiconductor manufacturing process, its description is omitted. Then, the color filter 104 is formed. Since this method is also performed in the conventional color filter manufacturing process, description thereof will be omitted.

After forming the color filter 104, a surface flattening layer 103 made of a low refractive index resin such as an acrylic resin is formed in order to flatten the irregularities of the color filter 104. Then, the surface flattening layer 1 is formed by the diffusion polymerization method.
A refractive index distribution is formed at a desired position on the surface of No. 03. The flatness of the surface of the refractive index distribution region 103a is within 0.2 μm within one region.

After forming the refractive index distribution region, the antireflection film 110 is formed on the surface of the surface flattening layer by a dipping method.
To form. As a material for the antireflection film, CYTOP (manufactured by Asahi Glass) containing a low-refractive-index fluororesin as an organic material is used, and a film having a refractive index of 1.34 is formed to a thickness of about 0.2 μm. The reflectance in the visible region of 700 nm could be 1.5% or less.

In this embodiment, the dipping method is used for forming the antireflection film, but a coating method such as a spin coating method other than the dipping method can be used.

Also in the present embodiment, it is possible to use an ion exchange method, a selective polymerization method or the like other than the diffusion polymerization method for forming the refractive index distribution region.

(Third Embodiment) Next, a third embodiment will be described in detail with reference to FIG. FIG. 2 shows a schematic sectional view of the third embodiment. 110 is an antireflection film, 101 is the surface of a color filter, and 104 is a color filter.
The color filter 104 is a light receiving unit (photoelectric conversion element) 10
9 is formed on the light incident side and is made of a low refractive index resin. A refractive index distribution region 104a is formed in the color filter 104 so as to correspond to the light receiving unit 109. 1
04b is a low refractive index resin region.

The refractive index distribution region 104a is a surface flattening layer 1
The refractive index gradually decreases while spreading from the upper side to the lower side of 04. The curve in FIG. 2 shows the situation. This refractive index distribution region functions as a microlens and collects incident light in the light receiving portion.

Although FIG. 2 shows that each region has a boundary, in reality, these regions do not have a clear boundary. Further, since the refractive index distribution region 104a is formed inside the color filter 104, its surface is substantially flat.

Reference numeral 105 is an in-layer flattening layer, 106 is a light-shielding film,
107 is an interlayer insulating layer, 108 is a wiring, and 109 is a light receiving portion. In this embodiment, the surface flattening layer 103 is not provided on the color filter 104.

The manufacturing method of this embodiment will be described below. First, the light receiving portion 109, the wiring 108, the interlayer insulating layer 107, and the light shielding layer 10 are formed on a wafer made of silicon or the like.
6. An in-layer flattening layer 105 is formed. Since this method is performed in the conventional semiconductor manufacturing process, its description is omitted. Then, the color filter 104 is formed. Since this method is also performed in the conventional color filter manufacturing process, description thereof will be omitted.

After forming the color filter 104, a refractive index distribution region is formed at a desired position on the surface of the color filter 104 by the diffusion polymerization method described above.

Then, after forming the refractive index distribution region, an antireflection film 110 is formed on the surface of the color filter 104 by a dipping method. As a material for the antireflection film, CYTOP (manufactured by Asahi Glass), which is an organic material containing a low-refractive-index fluororesin, is used, and a film having a refractive index of 1.34 is formed at a thickness of about 0.
By forming 2 μm, the reflectance in the visible region of 400 to 700 nm could be 1.5% or less.

In the present embodiment, the dipping method is used for forming the antireflection film, but a coating method such as a spin coating method other than the dipping method can be used.

As in the case of the first and second embodiments, it is possible to use an ion exchange method, a selective polymerization method or the like other than the diffusion polymerization method for forming the refractive index distribution region.

In the above embodiments, since the refractive index distribution region that functions as a microlens is formed on the surface flattening layer formed on the light incident side or the light incident surface of the color filter, the refractive index distribution region is formed on the surface of the surface. It is possible to reduce the distance from the light receiving portion and increase the numerical aperture, compared to the conventional case where a microlens is formed.

Further, since the antireflection film is formed on the planar layer, the optimum film thickness for the antireflection property is obtained as compared with the conventional case where the antireflection film is formed on the curved microlens. The design of can now be done easily.

Further, since the antireflection film is formed on a layer having a substantially flat surface and high flatness, the adhesion is improved as compared with the antireflection film formed on a microlens having a curved surface and minute irregularities. did.

Further, since the antireflection film is formed on the flat layer, cracks are less likely to occur in the antireflection film. Furthermore, when an organic material is used as the material of the antireflection film, cracks are less likely to occur.

Further, since it becomes possible to form the antireflection film by the spin coating method, the dipping method, etc., as compared with the case where it is formed by the vapor phase growth method which has been conventionally adopted as the forming method, It has become possible to significantly reduce the cost of forming it.

(Fourth Embodiment) FIG. 3 is a block diagram of a still video camera which is an example of a solid-state imaging system using the solid-state imaging device described in each of the above-described embodiments. The solid-state imaging device described in the above embodiment is the solid-state imaging device 204.
Is used as. In FIG. 3, the barrier 201 serves both as a lens protector and a main switch, and the lens 2
02 forms an optical image of a subject on the solid-state imaging device 204. The diaphragm 203 is for varying the amount of light that has passed through the lens, and the solid-state imaging device 204 is a device for taking in the subject formed by the lens 202 as an image signal. The image pickup signal processing circuit 205 performs various corrections, clamps, and other processing on the image signal output from the solid-state image pickup device 204,
The A / D converter 206 performs analog-digital conversion of the image signal output from the solid-state imaging device 204.

The signal processing unit 207 performs various corrections on the image data output from the A / D converter 206 and compresses the data. The timing generator 208 includes the solid-state imaging device 204, the imaging signal processing circuit 205, and the A / D converter 2.
06, outputs various timing signals to the signal processing unit 207, and the overall control / arithmetic unit 209 controls various arithmetic operations and the entire still video camera. The memory unit 210 is for temporarily storing image data, and is a recording medium control I / F.
The (interface) unit 211 is an interface for recording or reading on a recording medium. The recording medium 212 is a detachable semiconductor memory for recording or reading image data. The external I / F (interface) unit 213 is an interface for communicating with an external computer or the like.

Next, the operation of FIG. 3 will be described. When the barrier 201 is opened, the main power source is turned on, then the control system power source is turned on, and the image pickup system circuit such as the A / D converter 206 is turned on. Then, in order to control the exposure amount, the overall control / arithmetic unit 209 opens the diaphragm 203, and the signal output from the solid-state imaging device 204 is passed through the imaging signal processing circuit 205 to the A / D converter 206. Is output. The A / D converter 206 converts the signal into an A / D signal.
It is converted and output to the signal processing unit 207. Signal processing unit 2
In step 07, the overall control / calculation unit 209 calculates the exposure based on the data.

The brightness is determined based on the result of the photometry, and the overall control / calculation unit 209 controls the diaphragm according to the result. Next, based on the signal output from the solid-state imaging device 204, the overall control / calculation unit 209 extracts the high frequency component and calculates the distance to the subject. After that, the lens is driven to determine whether or not it is in focus. When it is determined that the lens is not in focus, the lens is driven again to measure the distance.

Then, after the focus is confirmed, the main exposure starts. When the exposure is completed, the image signal output from the solid-state image pickup device 204 is corrected in the image pickup signal processing circuit 205, further A / D converted by the A / D converter 206, and passes through the signal processing unit 207 to perform overall control. It is stored in the memory unit 210 by the operation 209. After that, the memory unit 21
The data stored in 0 passes through the recording medium control I / F unit 211 and is recorded on the removable recording medium 212 such as a semiconductor memory under the control of the overall control / arithmetic unit 209. Alternatively, the image may be processed by directly inputting it to a computer or the like through the external I / F unit 213.

[0047]

As described above, the present invention has the following effects. (1) Since the refractive index distribution region that functions as a microlens is formed on the surface of the flattening layer or color filter, it receives light more than in the conventional case where the microlens is formed on the flattening layer or color filter. It has become possible to increase the numerical aperture by increasing the distance from the part. (2) Since the antireflection film is formed on the planar layer, it is easier to optimally design the film thickness with respect to the antireflection property, as compared with the conventional case where the antireflection film is formed on the curved microlens. Now you can do it. (3) Since the antireflection film is formed on a layer having a substantially flat surface and high flatness, the adhesion to the microlens is better than that of the antireflection film formed on the microlens having a curved surface and minute irregularities. Has improved. (4) By forming the antireflection film on the planar layer, cracks were less likely to occur in the antireflection film. Furthermore, when an organic material is used as the material of the antireflection film,
Cracks became even less likely to occur. (5) Since the antireflection film can be formed by a coating method such as a spin coating method or a dipping method,
Compared with the case of forming by the conventional method, it has become possible to significantly reduce the cost at the time of forming.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of Embodiments 1 and 2 of the present invention.

FIG. 2 is a schematic cross-sectional view of Embodiment 3 of the present invention.

FIG. 3 is a configuration diagram of a fourth embodiment of the present invention.

[Explanation of symbols]

101 Color filter surface 102 surface of flattening layer 103 surface flattening layer 104 color filter 105 In-layer planarization layer 106 Light-shielding film 107 interlayer insulating film 108 wiring 109 Light receiving part 110 Anti-reflection film 201 Barrier 202 lens 203 aperture 204 Solid-state imaging device 205 image pickup signal processing circuit 206 A / D converter 207 Signal processing unit 208 Timing generator 209 Overall control / arithmetic unit 210 memory 211 Recording medium control I / F unit 212 recording medium 213 External I / F section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/335 G02B 1/10 A F term (reference) 2H048 BB02 BB08 BB10 BB28 BB47 2K009 AA07 CC03 CC26 DD02 4M118 AA01 AA05 AA10 AB01 BA06 CA02 CB13 EA01 GC07 GD04 GD10 5C024 CX41 CY47 EX43 EX52 5F088 BA03 BA20 BB03 EA04 HA01 HA05 HA10 HA20 JA12 JA13

Claims (9)

[Claims] 1. A solid-state imaging device comprising at least a light-receiving portion and a microlens, the surface of the microlens being in contact with a gas phase, wherein a flattening layer provided on the light-incident side of the light-receiving portion. In the solid-state image pickup device, the microlens is formed by forming a refractive index distribution corresponding to the light receiving portion. 2. A solid-state imaging device having at least a light-receiving portion, a planarization layer provided on the light-receiving portion, and a microlens, wherein the surface of the microlens is in contact with the gas phase. A solid-state imaging device, wherein the microlens is formed by forming a refractive index distribution in the flattening layer. 3. A light receiving unit, a color filter provided on the light receiving unit, and a microlens,
A solid-state imaging device configured such that a surface of the microlens is in contact with a gas phase, wherein the microlens is formed by forming a refractive index distribution in the color filter. 4. The solid-state imaging device according to claim 2, wherein the flattening layer is formed on a color filter. 5. The solid-state image pickup device according to claim 1, wherein an antireflection film is formed on the surface of the flattening layer or the color filter. 6. The solid-state imaging device according to claim 5, wherein the antireflection film is an organic material. 7. The solid-state imaging device according to claim 5, wherein the antireflection film is formed by a coating method. 8. The solid-state imaging device according to claim 7, wherein the coating method is a dipping method. 9. The solid-state imaging device according to claim 1, an optical system that forms an image of light on the solid-state imaging device, and signal processing that processes an output signal from the solid-state imaging device. A solid-state imaging system comprising: a circuit.