Solid-state imaging device with layered microlenses and method for manufacturing same

A solid-state imaging device with microlenses having a first lens layer and a second lens layer, the second lens layer being formed at least at a periphery of each microlens with either a portion of the second lens layer present at a central portion of each of the microlenses being thinner than a portion of the second lens layer present at the periphery of the microlens or no portion of the second lens layer being present at the central portion of each of the first microlenses. Between first pixel portions there is an interpixel gap, and the solid-state imaging device includes light blocking layers in alignment with the gaps.

FIELD

The technology of the present disclosure relates to a solid-state imaging device, a method for manufacturing the solid-state imaging device, and an electronic apparatus, and particularly to a solid-state imaging device including microlenses on photodiodes, a method for manufacturing the solid-state imaging device, and an electronic apparatus.

BACKGROUND

CMOS (complementary metal oxide semiconductor) solid-state imaging devices are known to be classified into a front-illumination type and a rear-illumination type. A solid-state imaging device of either of the two types includes a pixel region in which a plurality of unit pixels are formed on a semiconductor base substrate and each of the unit pixels is formed of a photodiode that works as a photoelectric converter and a plurality of pixel transistors.

In a front-illumination solid-state imaging device, the front surface of a substrate on which a multilayer wiring layer is formed works as a light receiving surface, and light is incident on the front surface of the substrate.

In a rear-illumination solid-state imaging device, the rear surface of the substrate that faces away from the front surface of the substrate on which a multilayer wiring layer and pixel transistors are formed works as a light receiving surface, and light is incident on the rear surface of the substrate.

The photodiodes are isolated from each other by a device isolating region formed of an impurity diffusion layer. Further, the multilayer wiring layer, in which a plurality of wiring lines are disposed, is formed via an interlayer insulating layer on the front surface of the semiconductor base substrate, on which the pixel transistors are formed.

In a front-illumination solid-state imaging device, the wiring lines are formed in regions other than the photodiodes. On-chip color filters and microlenses are sequentially formed via a planarization layer on the multilayer wiring layer. The on-chip filters are formed, for example, of an array of red (R), green (G), and blue (B) filters.

In a rear-illumination solid-state imaging device, the wiring lines can be formed irrespective of the positions of the photodiodes. An insulating layer, on-chip color filters, and microlenses are sequentially formed on the rear surface of the semiconductor base substrate, which works as the light receiving surface of the photodiodes.

In a rear-illumination solid-state imaging device, since the multilayer wiring layer does not constrain light from entering the photodiodes in any manner, each of the photodiodes can be provided with a large opening. Further, the distance from the photodiodes to the microlenses can be shortened, as compared with that in a front-illumination solid-state imaging device. Shortening the distance can improve the ability of the microlenses to collect light, whereby obliquely incident light can also be efficiently introduced. As a result, the sensitivity of the solid-state imaging device can be increased.

To improve the ability of the microlenses to collect light, for example, the curvature of each of the microlenses may be increased, or the refractive index of the material of which the microlenses are made may be increased (see JP-A-2007-53318, JP-A-1-10666, JP-A-2008-277800, and JP-A-2008-9079).

SUMMARY

The solid-state imaging device described above is typically required to improve their sensitivity characteristics by optimizing the shape of the microlenses.

Thus, it is desirable to provide a solid-state imaging device having excellent sensitivity characteristics, a method for manufacturing the solid-state imaging device, and an electronic apparatus using the solid-state imaging device by using the technology of the present disclosure.

An embodiment of the technology of the present disclosure is directed to a solid-state imaging device including a first lens layer and a second lens layer, and the second lens layer is formed at least at a periphery of each first microlens formed based on the first lens layer. The second lens layer present at a central portion of each of the first microlenses is thinner than the second lens layer present at the periphery of the first microlens, or no second lens layer is present at the central portion of each of the first microlenses.

Another embodiment of the technology of the present disclosure is directed to an electronic apparatus including the solid-state imaging device described above and a signal processing circuit that processes an output signal from the solid-state imaging device.

Still another embodiment of the technology of the present disclosure is directed to a method for manufacturing a solid-state imaging device including forming first microlenses having an inter-pixel gap therebetween based on a first lens layer, and forming a second lens layer at least at a periphery of each of the first microlenses. In the formation of the second lens layer, the second lens layer formed at a central portion of each of the first microlenses is thinner than the second lens layer formed at the periphery of the first microlens, or no second lens layer is present at the central portion of each of the first microlenses.

According to the solid-state imaging device described above and the solid-state imaging device manufactured using the manufacturing method described above, the first microlenses having an inter-pixel gap therebetween are formed based on the first lens layer, and the second lens layer is formed at the periphery of each of the first microlenses. The second lens layer formed at the periphery of each of the first microlenses fills the inter-pixel gap between the first microlenses. The area of each of the microlenses in a plan view is therefore enlarged, whereby the ability of the microlens to collect light is improved. As a result, the sensitivity characteristics of the solid-state imaging device are improved. An electronic apparatus having excellent sensitivity characteristics can thus be configured by incorporating the solid-state imaging device.

According to the embodiments of the technology of the present disclosure, a solid-state imaging device having excellent sensitivity characteristics, a method for manufacturing the solid-state imaging device, and an electronic apparatus can be provided.

DETAILED DESCRIPTION

An example of the mode for carrying out the technology of the present disclosure will be described below. It is, however, noted that the technology of the present disclosure is not limited to the following example.

The description will be made in the following order.

1. Embodiment of solid-state imaging device

2. Embodiment of method for manufacturing solid-state imaging device

3. Embodiment of electronic apparatus

1. Embodiment of Solid-State Imaging Device

Example of Configuration of Solid-State Imaging Device: Schematic Configuration Diagram

A specific form of a solid-state imaging device according to the present embodiment will be described below.

FIG. 1is a schematic configuration diagram showing a MOS (metal oxide semiconductor) solid-state imaging device as an example of the solid-state imaging device.

A solid-state imaging device10shown inFIG. 1is formed of a pixel section (what is called imaging region)13and a peripheral circuit section. In the pixel section13, pixels12, each of which includes a photodiode, are regularly and two-dimensionally arranged as a plurality of photoelectric converters on a silicon substrate or any other semiconductor base substrate. Each of the pixels12includes a photodiode and a plurality of pixel transistors (what is called MOS transistor).

The plurality of pixel transistors can be formed, for example, of three transistors: a transfer transistor; a rest transistor; and an amplification transistor. The plurality of pixel transistors can alternatively be formed of four transistors: those described above and an additional selection transistor.

The peripheral circuit section is formed of a vertical drive circuit14, column signal processing circuits15, a horizontal drive circuit16, an output circuit17, and a control circuit18.

The control circuit18produces a clock signal and a control signal based on a vertical sync signal, a horizontal sync signal, and a master clock, and the produced clock signal and control signal serve as references according to which the vertical drive circuit14, the column signal processing circuits15, the horizontal drive circuit16, and other components operate. The control circuit18inputs the signals into the vertical drive circuit14, the column signal processing circuits15, the horizontal drive circuit16, and other components.

The vertical drive circuit14is formed, for example of a shift resistor. The vertical drive circuit14selects and scans the pixels12in the pixel section13sequentially in the vertical direction on a row basis and supplies the column signal processing circuits15with pixel signals based on signal charge produced in accordance with the amount of light received by the photoelectric conversion devices in the selected pixels12via vertical signal lines19.

Each of the column signal processing circuits15is disposed in accordance with a certain unit of pixels12, for example, on a pixel column and performs noise reduction or otherwise processes signals outputted from the pixels12in a single row by using a signal from black reference pixels (formed around effective pixel region) on a pixel column basis. That is, the column signal processing circuits15perform CDS (correlated double sampling) for removing a fixed pattern noise specific to the pixels12, signal amplification, and other types of signal processing. Each of the column signal processing circuits15has a horizontal selection switch (not shown) provided at its output stage and connected to a horizontal signal line11.

The horizontal drive circuit16is formed, for example, of a shift resistor. The horizontal drive circuit16sequentially selects each of the column signal processing circuits15by successively outputting a horizontal scan pulse and outputs pixel signals from each of the column signal processing circuits15to the horizontal signal line11.

The output circuit17performs signal processing on the signals sequentially supplied from each of the column signal processing circuits15through the horizontal signal line11and outputs the processed signals.

When the solid-state imaging device10described above is used as a rear-illumination solid-state imaging device, no wiring layer is formed on the rear surface (what is called light receiving surface) on the side on which light is incident, but a wiring layer is formed on the front surface facing away from the light receiving surface.

Example of Configuration of Solid-State Imaging Device: Pixel Section

FIG. 2is a cross-sectional view showing a key portion that forms a single pixel of the solid-state imaging device according to the present embodiment.

A solid-state imaging device20shown inFIG. 2includes a plurality of photodiodes (PDs)22on the side of a semiconductor base substrate21on which light is incident. Each of the PDs22is formed in a unit pixel29of the solid-state imaging device20. An insulating layer23formed of a single layer or multiple layers is formed on the semiconductor base substrate21.

In the rear-illumination solid-state imaging device20shown inFIG. 2, a circuit section including a multilayer wiring layer and pixel transistors is formed on the surface facing away from the surface on which light is incident, but the configuration of the circuit section is omitted inFIG. 2.

The insulating layer23, when formed of a single layer, is made, for example, of SiO. The insulating layer23, when formed of multiple layers, is formed of multiple layers having different refractive indices based on the configuration of an antireflection layer. For example, the insulating layer23is formed of two layers: a hafnium oxide (HfO2) layer and a silicon oxide layer.

An inter-pixel light blocking layer24is formed on the insulating layer23described above, specifically, along the boundary between the unit pixels29in correspondence with an opening of each of the PDs22of the solid-state imaging device20. The inter-pixel light blocking layer24is formed, for example, of a layer made of W, Al, Cu, or any other suitable metal or carbon black, a titanium black, or any other suitable organic material. The inter-pixel light blocking layer24prevents incident light from leaking to an adjacent pixel and hence suppress color mixture in the solid-state imaging device20.

A first planarization layer25made, for example, of an acrylic resin is formed on the insulating layer23and the inter-pixel light blocking layer24. The first planarization layer25planarizes protrusions and recesses resulting from the inter-pixel light blocking layer24and other factors. The first planarization layer25further reduces application unevenness that occurs when color filters are formed on the semiconductor base substrate21, for example, in a spin application process.

Color filters26are formed on the first planarization layer25. The color filters26are formed of a variety of optical filters, such as RED, GREEN, BLUE, YELLOW, CYAN, MAGENTA optical filters. In the formation of the color filters26, the layer thickness for each of the colors is so optimized that an optimum color image is outputted. The surface of the entire color filters26therefore has protrusions and recesses to some extent.

A second planarization layer27for planarizing the protrusions and recesses resulting from the surfaces of the color filters26is formed on the color filters26. The second planarization layer27is made of a material that has thermal fluidity and thermal curability and forms a cured layer when a thermal treatment is finished, such as an acrylic resin, a styrene resin, and a styrene-acryl copolymerizing resin. The planarization ability of the materials described above decreases in the following order: an acrylic resin, a styrene-acryl copolymerizing resin, and a styrene resin. The second planarization layer27is therefore preferably made of an acrylic resin, which excels in the planarization ability.

A buffer layer28is formed on the second planarization layer27. The buffer layer28is made, for example, of SiO or SiON. The buffer layer28is formed to prevent corrugation due to the difference in film stress or reduce the reflectance, as will be described later.

Microlenses30are formed on the buffer layer28.

The microlenses30are formed of a first lens layer31and a second lens layer33formed on the first lens layer31. The first lens layer31is formed over the second planarization layer27and forms first microlenses32. The second lens layer33is then so formed that it covers the first microlenses32. The second planarization layer27is formed to increase uniformity of the first microlenses32formed over the color filters26.

The first lens layer31, which forms the microlenses30in the solid-state imaging device20, is made of one or more of the following materials: a resin, SiN, and SiON.

The resin is, for example, a metal-oxide-containing resin in which metal fine particles are dispersed. Examples of the resin in which metal fine particles are dispersed include an acrylic resin, a styrene-based resin, a novolac resin, an epoxy-based resin, a polyimide-based resin, and a siloxane-based resin. Examples of the metal fine particles that are dispersed in the resin include a zinc oxide, a zirconium oxide, a niobium oxide, a titanium oxide, and a tin oxide. Dispersing a metal oxide in a resin increases the refractive index of the resin.

When the first lens layer31is made of SiN and the second planarization layer27is made of an acrylic resin, formation of SiN directly on the second planarization layer27may produce corrugation along the interface between the two layers in some cases due to stress induced when the SiN layer is formed. Corrugation degrades an image produced by the solid-state imaging device.

Corrugation results from the difference in membrane stress between the resin that form the second planarization layer27, such as an acrylic resin, and the inorganic material that forms the first lens layer31, such as SiN.

The magnitude of the membrane stress induced in the materials described above increases in the following order: an acrylic resin (second planarization layer27), SiO, SiON, SiN (first lens layer31). Corrugation occurs because the difference in membrane stress between the second planarization layer27(acrylic resin) and the first lens layer31(SiN) is large as described above. To address the problem, the buffer layer28made of SiO or SiON, in which stress of intermediate magnitude is induced, is formed between the two layers. A buffering effect provided by the layer in which stress of intermediate magnitude is induced suppresses corrugation along the interface between the two layers.

The magnitude of the membrane stress induced in an acrylic resin, a styrene resin, and a styrene-acryl copolymerization resin is as follows: acrylic resin<styrene-acryl copolymerization resin<styrene resin<SiO. A styrene resin and a styrene-acryl copolymerization resin are more similar to SiN, which forms the first lens layer31, than an acrylic resin. Corrugation is therefore more unlikely to occur along the interface when a styrene resin or a styrene-acryl copolymerization resin as a second planarization layer27, in which a greater amount of membrane stress is induced than in an acrylic resin, is used than when an acrylic resin is used.

Even when the first lens layer31is made of a metal-oxide-containing resin or corrugation is unlikely to occur along the interface between the first lens layer31and the second planarization layer27, the buffer layer28described above can be provided as an antireflection layer.

Consider now a case where the second planarization layer27made of an acrylic resin, the buffer layer28made of SiON, and the first lens layer31made of SiN are formed over the color filters26.

In the configuration described above, the magnitude of the refractive indices n of the layers is as follows: second planarization layer27(acrylic resin: n is about 1.5)<buffer layer28(SiON: n ranges from about 1.6 to 1.8)<first lens layer31(SiN: n ranges from about 1.85 to 2.0).

When the second planarization layer27is alternatively made of a styrene resin (n is about 1.6) or a styrene-acryl copolymerization resin (n ranges from about 1.55 to 1.58) as well, the magnitude of the refractive indices n of the layers is as follows: second planarization layer27<buffer layer28(SiON)<first lens layer31(SiN).

The relationships of the magnitude of the refractive index described above indicate that when the buffer layer28is made of SiON, the reflectance decreases because the buffer layer28has an intermediate refractive index between those of the second planarization layer27and the first lens layer31.

As described above, the buffer layer28can function as an antireflection layer by employing a configuration in which the buffer layer28has an intermediate refractive index between those of the second planarization layer27and the first lens layer31. For example, even when the buffer layer28is made of SiO having a refractive index n of about 1.45, the buffer layer28can function as an antireflection layer by changing the materials, film formation conditions, and other factors of the second planarization layer27and the first lens layer31to adjust the refractive indices thereof.

Even when the first lens layer31is not made of SiN but is made of a metal-oxide-containing resin having a refractive index comparable with that of SiN, the reflectance can be reduced as described above.

When the second planarization layer27and the buffer layer28, the latter of which is made of SiN or SiON, are formed over the color filters26, the distance from the photodiodes22to the microlenses30in the solid-state imaging device20increases. The buffer layer28, however, only needs to be about 5 nm in thickness to provide the buffering effect. Further, the second planarization layer27can be formed to be thin when a selected acrylic resin has thermal fluidity, thermal curability, and thermal shrinkability. Therefore, even when the second planarization layer27and the buffer layer28are formed, and the distance from the photodiodes22to the microlenses30increases, the resultant decrease in the sensitivity of the solid-state imaging device does not cause a practical problem.

FIG. 3is a plan view showing the first lens layer31formed on the buffer layer28.

The broken lines shown inFIG. 3represent the unit pixels29in the solid-state imaging device20. The microlenses30formed in correspondence with the unit pixels29are preferably so formed that each of the microlenses30has the same size as that of the corresponding unit pixel29in the plan view. Further, the first lens layer31is so formed that it covers the entire unit pixels29.

The first microlenses32formed based on the first lens layer31are so formed that adjacent first microlenses32have a gap in at least one of the direction parallel to horizontally or vertically adjacent pixels (W1) and the direction parallel to diagonally adjacent pixels (W2), as shown inFIG. 3.

To improve the sensitivity characteristics of the solid-state imaging device20, the gaps between adjacent pixels in the directions W1and W2described above and the distance from the photodiodes22to the microlenses30are preferably minimized. Further, when the microlenses30are formed in a dry etching process, it is necessary to minimize the etching process period. The reason for this is that dark current in the solid-state imaging device20can be suppressed by minimizing plasma damage to the semiconductor base substrate21.

A typical solid-state imaging device of related art has square unit pixels29, as shown inFIG. 3described above. In this configuration, even when the first microlenses32are formed, for example, with no gap in the direction W1, the gaps in the direction W2, each of which is inherently large, still remain. When the microlenses30are formed, for example, in a dry etching process, it is conceivable that the gaps in the direction W2are eliminated by performing the etching in a condition that reduces the length of the gaps in the direction W2. When the dry etching is performed in a condition that eliminates the gaps in the direction W2, however, the dry etching period increases, resulting in degradation in dark current characteristics of the solid-state imaging device20. Further, when the processing period increases, wafer-to-wafer etching variation increases. As a result, the cross-sectional shape of the microlenses30varies, which adversely affects the sensitivity characteristics of the solid-state imaging device20.

In contrast, in the solid-state imaging device20according to the present embodiment, the microlenses30are formed by stacking the first lens layer31and the second lens layer33.

Now, define the thickness of the second lens layer33formed on the first lens layer31as follows: Let Tt be the thickness of the second lens layer33formed at a central portion of each of the first microlenses32, and let Tb be the thickness of the second lens layer33formed at the periphery of the first microlens32, as shown inFIGS. 4A to 4D. The thus defined Tt and Tb satisfy the following relationship: 0≦Tt≦Tb, which represents a configuration in which the second lens layer33is present at the periphery of each of the first microlenses32and the second lens layer33whose thickness is smaller than that of the second lens layer33present in the periphery is also present at the central portion of the first microlens32or no second lens layer33is present at the central portion of the first microlenses32.

In the thus configured solid-state imaging device20, the first microlenses32are so formed that adjacent ones have a gap w in at least one of the direction parallel to horizontally or vertically adjacent pixels (W1) and the direction parallel to diagonally adjacent pixels (W2), as shown inFIG. 3described above. In the condition that allows the gap w to be formed, the dry etching period can be shortened, whereby the increase in dark current in the solid-state imaging device20is suppressed.

Further, the microlenses30are so formed that the second lens layer33enlarges the area of each of the first microlenses32in the plan view. As a result, the ability of each of the microlenses30to collect light can be improved, whereby the sensitivity and shading characteristics of the solid-state imaging device20can be improved.

The second lens layer33is made of at least one of the materials selected from SiON, SiN, SiO, and SiOC (having refractive index of about 1.4). When the second lens layer33is made of SiO or SiOC, which has a refractive index lower than those of SiON and SiN, one of which forms the first lens layer31, the second lens layer33also functions as an antireflection layer on the microlenses30.

FIGS. 4A to 4Dshow configurations that satisfy the relationship between Tt and Tb described above, 0≦T≦tTb, in the first lens layer31and the second lens layer33, which form the microlenses30.

Microlenses30A to30D shown inFIGS. 4A to 4Dcorrespond to states in which second lens layers33having different thicknesses are formed on the first microlenses32. The microlenses30A to30D shown inFIGS. 4A to 4Dare so configured that the first microlenses32are formed based on the first lens layer31in a known method of related art and the second lens layer33is then so formed on the first lens microlenses32that the thickness of the second lens layer33is adjusted in a dry etching process. The method for forming the first lens layer31and the second lens layer33will be described in detail in the description of a method for manufacturing the solid-state imaging device, which will be described later.

In the microlenses30A shown inFIG. 4A, the second lens layer33is formed over the entire surface of the first lens layer31. The relationship between the thickness Tt of the second lens layer33at the central portion of each of the first microlenses32and the thickness Tb of the second lens layer33at the periphery of the first microlens32is Tt<Tb.

Further, the second lens layer33is so configured that it is thinnest at the central portion of each of the first microlenses32and gradually becomes thicker with the distance from the central portion toward the periphery.

In the configuration described above, the second lens layer33fills the inter-pixel gap w between the first microlenses32, whereby the resultant microlenses30A have no inter-pixel gap w. The area of each of the microlenses30A in a plan view can therefore be enlarged, whereby the ability of the microlens30A to collect light can be improved and the sensitivity characteristics of the solid-state imaging device20can be improved accordingly.

In the microlenses30B shown inFIG. 4B, the second lens layer33is formed over the entire surface of the first lens layer31except the central portion of each of the first microlenses32. The configuration corresponds to a state in which the etching is terminated when Tt becomes zero in the formation of the second lens layer33. The thus configured microlenses30B are formed based on the microlenses30A in the state shown inFIG. 4Aby further etching the second lens layer33.

The second lens layer33is not present at the central portion of each of the first microlenses32but is present at the periphery of the first microlens32. That is, the second lens layer33is formed based on the relationship of 0=Tt<Tb.

In the configuration described above, the second lens layer33formed at the periphery of each of the first microlenses32fills the inter-pixel gap w. The resultant microlenses30B have no inter-pixel gap w. The configuration described above allows the area of each of the microlenses30B in a plan view to be enlarged, whereby the ability of the microlens30B to collect light can be improved and the sensitivity characteristics of the solid-state imaging device20can be improved accordingly.

The microlenses30C shown inFIG. 4Ccorrespond to a state in which the second lens layer33is further etched from the microlenses30B in the state shown inFIG. 4B.

In the microlenses30C, the second lens layer33is formed over the entire surface of the first lens layer31except a central portion of each of the first microlenses32. The central portion of each of the first microlenses32and therearound is etched along with the second lens layer33by further etching the second lens layer33. InFIG. 4C, the broken lines32A each represent the portion of the lens surface of the central portion of the first microlens32before etched.

The configuration shown inFIG. 4Cis achieved by further etching the second lens layer33from the state in which the central portion of each of the first microlenses32is exposed to a state in which the first microlens32exposed through the second lens layer33is etched. As described above, each of the etched regions of the first lens layer31is enlarged in the direction from the central portion of the corresponding first microlens32toward the periphery thereof by further etching the second lens layer33.

In the configuration of the microlenses30C shown in FIG.4C as well, the second lens layer33is not present at the central portion of each of the first microlenses32but is present at the periphery of the first microlens32. That is, the second lens layer33is formed based on the relationship 0=Tt<Tb. The second lens layer33at the periphery of each of the first microlenses32fills the inter-pixel gap w. The resultant microlenses30C have no inter-pixel gap w.

As shown inFIG. 4C, even in the configuration in which no second lens layer33is formed at the central portion of each of the first microlenses32and therearound, the area of each of the microlenses30C in a plan view can be enlarged because the second lens layer33fills the inter-pixel gap w.

Further, even in the configuration in which the central portion of each of the first microlenses32is etched, the second lens layer33forms a series of lens surfaces formed of the first microlenses32and the second lens layer33.

The configuration described above allows the ability of each of the microlenses30to collect light to be improved and the sensitivity characteristics of the solid-state imaging device20to be improved accordingly.

The microlenses30D shown inFIG. 4Dcorrespond to a state in which the first lens layer31and the second lens layer33are further etched from the microlenses30C in the state of shown inFIG. 4C. InFIG. 4D, the broken lines32A each represent the portion of the lens surface of the first microlens32before etched.

In the microlenses30D, the second lens layer33is formed only in the vicinity of the periphery of each of the first microlenses32and in the inter-pixel gap w therearound. The etched region of each of the first microlenses32is enlarged in the direction from the center toward the periphery and is larger than the etched region in the configuration shown inFIG. 4Cdescribed above. Further, a central portion of each of the inter-pixel gaps w of the first lens layer31is etched away, as a central portion of each of the first microlenses32is. That is, the second lens layer33is completely etched away at the central portion of each of the inter-pixel gaps w, and the first lens layer31exposed through the second lens layer33at the central portion of the inter-pixel gap w is also etched.

In the configuration of the microlenses30D shown inFIG. 4D, the second lens layer33is not present at the central portion of each of the first microlenses32or the central portion of each of the inter-pixel gaps w. The second lens layer33having the thickness Tb is, however, present at the periphery of each of the first microlenses32. That is, the second lens layer33is formed based on the relationship 0=Tt<Tb.

Further, the surface formed by etching the first lens layer31at the central portion of each of the inter-pixel gaps w is connected to the surface of the second lens layer33and the lens surface of the adjacent first microlens32, whereby a series of lens surfaces that form the microlenses30D is formed.

As a result, the first microlenses32, the second lens layer33at the peripheries of the first microlenses32, and the etched surfaces of the inter-pixel gaps w of the first lens layer31form the microlenses30D with no inter-pixel gap w.

As described above, even in the configuration in which the first lens layer31formed in the inter-pixel gaps w is also etched, the second lens layer33formed at the periphery of each of the first microlenses32fills the inter-pixel gap w around the first microlens32. As a result, the area of each of the microlenses30D in a plan view is enlarged, whereby the ability of the microlens30to collect light can be improved and the sensitivity characteristics of the solid-state imaging device20can be improved accordingly.

The configuration of the microlenses30D shown inFIG. 4Dmay be further so etched that the bottom of the first lens layer31in each of the inter-pixel gaps w is penetrated to the second planarization layer27. In this configuration as well, as long as the second lens layer33having the thickness Tb is present at the periphery of each of the first microlenses32, the first microlenses32, the second lens layer33, and the first lens layer31in the inter-pixel gaps w form a series of lens surfaces, whereby the area of each of the microlenses30D in a plan view can be enlarged.

Variations of the microlenses in the solid-state imaging device described above will next be described.FIGS. 5A to 5Cshow the configurations of microlenses35of the variations. The components other than the microlenses are the same as those in the embodiment described above and will therefore not be illustrated or described.

The microlenses35shown inFIGS. 5A to 5Ceach include a third lens layer34over the first lens layer31and the second lens layer33.

The configuration of microlenses35A shown inFIG. 5Acorresponds to the configuration of the microlenses30A shown inFIG. 4Adescribed above, and the configuration of microlenses35B shown inFIG. 5Bcorresponds to the configuration of the microlenses30B shown inFIG. 4Bdescribed above.

In the microlenses35A shown inFIG. 5A, the third lens layer34is formed over the entire surface of the second lens layer33.

In the microlenses35B shown inFIG. 5B, the third lens layer34is so formed that is covers a central portion of each of the first microlenses32and the second lens layer33.

The third lens layer34is formed to a substantially uniform thickness along the upper surface of the second lens layer33both in the microlenses35A and the microlenses35B.

In the microlenses35C shown inFIG. 5C, the third lens layer34is provided over the first lens layer31and the second lens layer33and has a flat surface. The third lens layer34may thus have a flat surface.

Each of the third lens layers34shown inFIGS. 5A to 5C, when made of a material having a refractive index lower than that of the material that forms the first lens layer31, functions as an antireflection layer on the surface of the microlenses35.

Table 1 below shows the relationship of the refractive indices of the second lens layer33and the third lens layer34with the refractive index of the first lens layer31made of SiON or SiN.

In Table 1, it is assumed that the first lens layer31has a refractive index c, and the second lens layer33is made of a material (1) having a refractive index comparable with the refractive index c of the first lens layer31or a material (2) having a refractive index higher than the refractive index c of the first lens layer31. The third lens layer34is made of a material having a refractive index lower than the refractive index c of the first lens layer31.

In the configuration shown in the row (1) in Table 1, the third lens layer34functions as a monolayer antireflection layer. To this end, the third lens layer34is made of SiO (refractive index of about 1.45) or SiOC (refractive index of about 1.4).

In the configuration shown in the row (2) in Table 1, the second lens layer33and the third lens layer34function as a two-layer antireflection layer. To this end, the third lens layer34is made of SiO or SiOC, as in the configuration (1) described above.

For example, when the first lens layer31is made of SiON, the second lens layer33is made of SiON having the same refractive index as the refractive index of SiON, which forms the first lens layer31, or SiN having a refractive index higher than the refractive index of SiON, which forms the first lens layer31. The third lens layer34is made of SiOC or SiO having a refractive index lower than the refractive index of SiON, which forms the first lens layer31.

When the first lens layer31is made of SiN, the second lens layer33is made of SiN having the same refractive index as the refractive index of SiN, which forms the first lens layer31. The third lens layer34is made of SiOC or SiO having a refractive index lower than the refractive index of SiN, which forms the first lens layer31.

The refractive index of the material that forms each of the lens layers is determined by a variety of film formation conditions in a P-CVD process (plasma CVD, plasma-enhanced chemical vapor deposition), such as the temperature, the pressure, the type of gas, and the flow rate of the gas. The refractive indices of the first lens layer31and the second lens layer33are adjusted to be higher than the refractive index of a typical microlens resin material (ranging from about 1.5 to 1.6) in order to improve the ability of the microlenses30to collect light.

When the second lens layer33and the third lens layer34function as a two-layer antireflection layer, the second lens layer33is made of a high refractive index material, and the third lens layer34is made of a low refractive index material. The high refractive index material that forms the second lens layer33is a material having a refractive index higher than the refractive index of SiN, such as a zirconium oxide (ZrO having a refractive index n of 2.4) or a titanium oxide (TiO having a refractive index n of 2.52). The low refractive index material that forms the third lens layer34is a material having a refractive index lower than the refractive index of SiOC, such as a magnesium fluoride (MgF2having a refractive index n of 1.37). Each of the second lens layer33and the third lens layer34is formed to a thickness of 1.0/4λ, where λ represents the wavelength of desired light to be reflected.

2. Method for Manufacturing Solid-State Imaging Device

A description will next be made of a method for manufacturing the solid-state imaging device according to the embodiment described above. In the following description, only the components located above the color filters in the solid-state imaging device are shown, and the other components are omitted. The components located below the color filters can be manufactured by using a method for manufacturing a solid-state imaging device known in related art. Further, the solid-state imaging device described below has a configuration in which no buffer layer is provided between the second planarization layer and the first lens layer.

First, the color filters26to be formed in correspondence with the pixels of the solid-state imaging device are formed, as shown inFIG. 6A. The color filters26are formed by using a coloring agent, for example, a pigment or a photosensitive resin into which a pigment is added, in a photolithography process. The color filters26are made of RED, GREEN, BLUE, YELLOW, CYAN, and MAGENTA and other color materials.

The second planarization layer27is then formed on the color filters26, as shown inFIG. 6B. The second planarization layer27is made of a material that has thermal fluidity and thermal curability and forms a cured layer when a thermal treatment is finished, such as an acrylic resin, a styrene resin, and a styrene-acryl copolymerizing resin. A method for forming the second planarization layer27will be described later in detail.

The first lens layer31made, for example, of SiN is then formed on the second planarization layer27, as shown inFIG. 6C. The first lens layer31is formed to be sufficiently thicker than the first microlenses32to be formed. The first lens layer31is formed, for example, in a P-CVD process using SiH4, NH3, and N2as film formation gases. The pressure and other parameters are adjusted as appropriate at a temperature of about 200° C. in the P-CVD formation process.

A positive photosensitive resin41is formed on the first lens layer31and patterned in correspondence with the pixels of the solid-state imaging device20, as shown inFIG. 6D. Examples of the positive photosensitive resin41include a novolac resin, a styrene-based resin, and a copolymerizing resin formed thereof. The photosensitive resin41is formed and patterned, for example, by performing the following processes: spin application; pre-baking; i-line light exposure; post-exposure baking, development, and post-baking processing in this order. In the post-baking processing, the photosensitive resin41having the lens shape shown inFIG. 6Dis formed.

The positive photosensitive resin41described above is then used as a mask to transfer the lens shape made of the photosensitive resin41to the first lens layer31in an etching process. The first microlenses32are thus formed, as shown inFIG. 7E. The first lens layer31is etched, for example, by using an ICP (inductively coupled plasma) apparatus, a CCP (capacitively coupled plasma) apparatus, a TCP (transformer coupled plasma) apparatus, a magnetron RIE (reactive ion etching) apparatus, an ECR (electron cyclotron resonance) apparatus, or any other suitable plasma generating apparatus. The temperature, the pressure, and other parameters are then adjusted as appropriate, and an etching gas primarily made of CF4, C4F8, or any other fluoro-carbon-based gas is used.

A plan view of the first lens layer31to which the lens shape shown inFIG. 7Ehas been transferred shows that the inter-pixel gaps w are present in at least one of the directions W1and W2associated with the first microlenses32, as shown inFIG. 3described above. The etching can be finished in a short period by forming the first lens layer31in a condition that allows the inter-pixel gaps w to be present as described above. Since the dry etching period can be shortened, an increase in dark current in the solid-state imaging device20due to plasma damage can be suppressed.

The second lens layer33is then formed on the first lens layer31, as shown inFIG. 7F. The second lens layer33formed on the first microlenses32follows the shape of the lens surfaces of the first microlenses32. Further, the second lens layer33formed on the inter-pixel gaps w is thicker than the second lens layer33formed on the first microlenses32.

The second lens layer33is made, for example, of SiN and formed in a P-CVD process by using SiH4, NH3, and N2as gases for forming an SiN film. The pressure and other parameters are adjusted as appropriate at a temperature of about 200° C. in the P-CVD formation process.

The thus formed second lens layer33is then etched to form the second lens layer33having the configuration shown inFIG. 7Gor7H.

FIG. 7Gcorresponds to the configuration of the microlenses30A shown inFIG. 4Adescribed above, in which the second lens layer33is formed over the entire surface of the first lens layer31. The second lens layer33is thinnest at the central portion of each of the first microlenses32, and the layer thickness gradually increases from the central portion toward the periphery.

The second lens layer33fills the inter-pixel gaps w between the first microlenses32. The microlenses30are thus formed.

FIG. 7Hcorresponds to the configuration of the microlenses30B shown inFIG. 4Bdescribed above, in which the second lens layer33is formed over the entire surface of the first lens layer31except the central portion of each of the first microlenses32. The etching of the second lens layer33is terminated when the layer thickness at the central portion of each of the first microlenses32becomes zero.

As shown inFIGS. 7G and 7H, the second lens layer33formed at the periphery of each of the first microlenses32fills the inter-pixel gap w, and the resultant microlenses30have no inter-pixel gap w.

Although not shown, the configuration of the microlenses30C shown inFIG. 4Cdescribed above and the configuration of the microlenses30D shown inFIG. 4Ddescribed above can also be achieved by changing the etching conditions as appropriate.

The solid-state imaging device20including the microlenses30shown inFIG. 2described above can be manufactured by carrying out the steps described above.

According to the manufacturing method described above, the first microlenses32are formed with the inter-pixel gaps w present in at least one of the direction parallel to horizontally or vertically adjacent pixels (W1) and the direction parallel to diagonally adjacent pixels (W2). In the condition that allows the inter-pixel gaps w to be formed, the dry etching period can be shortened, whereby an increase in dark current in the solid-state imaging device20is suppressed. Further, the second lens layer33fills the inter-pixel gaps w and the resultant microlenses30have no inter-pixel gap w, whereby the area of each of the microlenses30in a plan view is enlarged and the ability of the microlens30to collect light is improved accordingly. As a result, the sensitivity and shading characteristics of the solid-state imaging device20can be improved.

[Method for Forming Second Planarization Layer]

A description will be made of a method for forming the second planarization layer27formed on the color filters26in the method for manufacturing the solid-state imaging device described above.

To increase the sensitivity of the solid-state imaging device20, it is preferable to shorten the distance between the microlenses30and the photodiodes22. To this end, each of the layers on the semiconductor base substrate21shown inFIG. 2described above is desirably formed to be thin. The second planarization layer27, when formed, is also desirably formed to be thin.

To reduce the thickness of the second planarization layer27, the second planarization layer27is made of a material that has thermal fluidity and thermal curability and forms a cured layer when a thermal treatment is finished, such as an acrylic resin, a styrene resin, and a styrene-acryl copolymerizing resin.

FIGS. 8A to 8Cshow steps of forming the second planarization layer27with a resin having the characteristics described above.

First, a resin is applied onto the color filters26in a spin application process to form a second planarization layer27A, as shown inFIG. 8A. The second planarization layer27A immediately after the application has irregularities in the surface because affected by the protrusions and recesses in the surfaces of the color filters26having different thicknesses for different colors.

The second planarization layer27A in the state shown inFIG. 8Ais then heat treated. Since the resin that forms the second planarization layer27A has thermal fluidity and thermal curability as described above, the heat treatment increases the fluidity of the second planarization layer27A, which therefore moves in such a way that the surface thereof is planarized. As a result, a second planarization layer27B having recesses shallower than those before the protrusions and recesses undergo the heat treatment is formed, as shown inFIG. 8B.

FIG. 8Cshows the second planarization layer27cured by the heat treatment described above. The heat treatment also increases thermal curability of the second planarization layer27as well as the thermal fluidity thereof. The second planarization layer27further experiences thermal shrinkage in the heat treatment. The volume of the second planarization layer27therefore decreases from that before cure to that after cure because the second planarization layer27shrinks when it thermally cures. As a result, the cured second planarization layer27is thinner than the second planarization layer27before cure. The increase in fluidity resulting from the heat treatment further planarizes the surface of the second planarization layer27.

Therefore, forming the second planarization layer27with a material that has thermal fluidity and thermal curability and forms a cured layer when a thermal treatment is finished reduces the amount of irregularities produced immediately after the spin application, whereby a substantially flat, thin, thermally cured layer can be formed.

Further, the second planarization layer27, which is made, for example, of an acrylic resin, a styrene resin, or a styrene-acryl copolymerizing resin, which experiences increases in thermal fluidity and thermally curability at the same time, can be formed to be further thinner by reducing the molecular weight of the resin to increase the amount of thermal shrinkage. The thus formed thin second planarization layer27reduces the distance between the photodiodes22and the microlenses30, whereby the sensitivity characteristics of the solid-state imaging device20are improved.

[Etching Transfer to First Lens Layer]

A description will be made of the step of transferring the lens shape made of the photosensitive resin41to the first lens layer31shown inFIGS. 6D and 7Ein the method for manufacturing the solid-state imaging device described above.

The etching transfer described above is preferably performed in a condition that allows the material of the first lens layer31to be etched at the same speed as the photosensitive resin41formed on the first lens layer31is etched.

FIG. 9shows not only a state in which the photosensitive resin41having the microlens shape is formed on the first lens layer31but also the shape of the first microlenses32transferred to the first lens layer31in the etching transfer process. InFIG. 9, h1represents the height (thickness) of the central portion of the lens shape made of the photosensitive resin41and w3represents the inter-pixel gap of the lens shape. Further, h2represents the height (thickness) of the central portion of each of the first microlenses32, and w4and w5represent the inter-pixel gap between the first microlenses32.

When the first lens layer31is made of SiN, the etching is performed in a condition that allows (speed at which SiN is etched):(speed at which photosensitive resin41is etched) to be 1:1. The shape of the first microlenses32formed in this process is indicated by the broken line32A inFIG. 9. When the ratio of the etching speed between the first lens layer31and the photosensitive resin41is 1:1, the shape of the first microlenses32after the etching is substantially the same as the shape of the photosensitive resin41. As a result, the central portion of each of the first microlenses32is formed to a height h2equal to the height h1of the photosensitive resin41. The first microlenses32are also formed to have an inter-pixel gap w4equal to the inter-pixel gap w3of the photosensitive resin41.

Further, when a gas having strong etching deposition, such as C4F8, is used in the etching transfer process described above, the speed at which the first lens layer31is etched decreases because the ratio of the etching speed between the first lens layer31and the photosensitive resin41is shifted from 1:1. The solid line inFIG. 9represents the shape of the first microlenses32formed under the condition described above.

When the first microlenses32are etched to the height h2under the condition described above, the inter-pixel gap w5is smaller than that achieved when the etching ratio is 1:1. That is, the inter-pixel gap w5between the first microlenses and the inter-pixel gap w3associated with the photosensitive resin41satisfy the relationship of w3>w5.

Since the inter-pixel gap w5between the first microlenses32is small, the second lens layer formed on the first lens layer31can be thinner but can still fill the inter-pixel gap w5.

Further, when the speed at which the first lens layer31is etched relatively decreases, the etching process period increases, which raises a concern about an increase in plasma damage to the solid-state imaging device20. To reduced the plasma damage, it is necessary to increase the etching speed. In this case, the flow rate of the C4F8gas is reduced or a variety of etching conditions are so adjusted that the speed at which the first lens layer31is etched is greater than the speed at which the photosensitive resin41is etched with a gas type of C4F8still used. As a result, degradation in dark current characteristics due to plasma damage to the solid-state imaging device20and a decrease in productivity thereof can be suppressed.

A description will further be made of a case where the etching is performed in a condition that allows the speed at which the first lens layer31is etched to be relatively so increased that the relationship among the widths w3, w4, and w5is changed from w3>w4(w5) to w3<w4(w5). When the etching is performed in the condition that allows the gap associated with the first lens layer31increases, the etched first lens layer31may have an aspheric shape shown inFIG. 10in some cases because the first lens layer31(for example, SiN) is etched at a high speed. In this case, each of the first microlenses32has a shape similar to a cone having a round vertex, and the inter-pixel gap w widens, resulting in an imperfect arcuate curved portion y.

As described above, even when each of the first microlenses32is formed to have a conical shape, the second lens layer33is formed on the first lens layer31in the microlenses according to the present embodiment. As a result, even when each of the first microlenses32has an aspheric shape, the surface of each of the microlenses30can be so corrected by optimizing the lens shape of the second lens layer33that the aspheric shape approaches a spherical shape as shown inFIG. 10.

Therefore, even when there is a decrease in light collecting ability resulting from the shape of the first microlenses32, the ability of the microlenses30to collect light can be improved by forming the second lens layer33.

[Conditions Under which Second Lens Layer is Formed]

A description will be made of the relationship between the conditions under which the second lens layer33is formed and the curvature of the lens shape of the surface of the second lens layer33to be formed.

FIGS. 11A and 11Bshow a method for forming the second lens layer33with SiN or SiON, and a variety of specific conditions under which the mean free path is adjusted to adjust the curvature of the microlenses30in a P-CVD process are shown below.

The pressure at the time of film formation is adjusted to be a value between about 2 mTorr to 10 Torr. The mean free path increases as the pressure decreases, whereas decreasing as the pressure increases. That is, the mean free path is long when the pressure is 2 mTorr, whereas being short when the pressure is 10 Torr.

FIG. 11Ashows the configuration in a case where the second lens layer33is formed in a condition where the pressure at the time of film formation is low and hence the mean free path is long. On the other hand,FIG. 11Bshows the configuration in a case where the second lens layer33is formed in a condition where the pressure at the time of film formation is high and hence the mean free path is short.

The curvature of the surface of the second lens layer33decreases when the mean free path is long, as shown inFIG. 11A. On the other hand, the curvature of the surface of the second lens layer33increases when the mean free path is short, as shown inFIG. 11B.

When the second lens layer33at a central portion of each of the first microlenses32has the same thickness Tt in both cases, the second lens layer33at the periphery of the first microlens32therefore has a large thickness Tb inFIG. 11A, in which the mean free path is long. On the other hand, the second lens layer33at the periphery of the first microlens32has a small thickness Tb inFIG. 11B, in which the mean free path is short.

The ratio between the thicknesses of the second lens layer33at the central portion and the periphery (Tt/Tb) is greater when the pressure at the time of film formation is high than when the pressure at the time of film formation is low.

As described above, a desired shape can be formed, for example, the microlenses30can be formed in desired positions in the solid-state imaging device20and the microlenses30can have desired curvature, by adjusting the conditions under which the second lens layer33is formed.

Further, even when the first lens layer31is formed to have an aspheric shape as shown inFIG. 10described above, the aspheric shape can be corrected to a nearly spherical shape by adjusting the conditions under which the second lens layer33is formed as described above.

Although not described in the manufacturing method described above, the buffer layer28shown inFIG. 2may be formed on the second planarization layer27. In this case, the buffer layer28is made, for example, of SiO or SiON in a P-CVD process.

When the buffer layer28is made of SiO, SiH4, N2O, and other gases are used as the film formation gases. When the buffer layer28is made of SiON, SiH4, NH3, N2O, N2, and other gases are used as the film formation gases. The pressure and other parameters are adjusted as appropriate at a temperature of about 200° C. The temperature is determined also in consideration of color bleaching of the color filters26and the heat resistance of the organic material that forms the first planarization layer25and other layers.

The above embodiment has been described with reference to the case where the microlenses are used with a rear-illumination solid-state imaging device, but the microlenses described above can be used with a front-illumination CMOS solid-state imaging device and CCD solid-state imaging device.

3. Electronic Apparatus

A description will next be made of an embodiment of an electronic apparatus including the solid-state imaging device described above.

The solid-state imaging device described above can be used in a camera system, such as a digital camera and a video camcorder; a mobile phone having an imaging capability; and other electronic apparatus having an imaging capability.FIG. 12shows a schematic configuration of an apparatus in which the solid-state imaging device is used with a camera capable of capturing a still image or video images as an example of an electronic apparatus.

A camera50in this example includes a solid-state imaging device51, an optical system52that guides incident light to a light receiving sensor portion of the solid-state imaging device51, a shutter53provided between the solid-state imaging device51and the optical system52, and a drive circuit54that drives the solid-state imaging device51. The camera50further includes a signal processing circuit55that processes an output signal from the solid-state imaging device51.

The solid-state imaging device51can be either of the solid-state imaging devices of the embodiment described above and a second embodiment. The optical system (optical lens)52focuses image light (incident light) from a subject on an imaging surface (not shown) of the solid-state imaging device51. Signal charge is thus accumulated for a fixed period in the solid-state imaging device51. The optical system52may be formed of an optical lens group including a plurality of optical lenses. The shutter53controls a period during which the solid-state imaging device51is illuminated with the incident light and a period during which the incident light to the solid-state imaging device51is blocked.

The drive circuit54supplies drive signals to the solid-state imaging device51and the shutter53. Using the supplied drive signals, the drive circuit54controls signal output operation of the solid-state imaging device51to the signal processing circuit55and shuttering operation of the shutter53. That is, in this example, one of the drive signals (timing signal) supplied from the drive circuit54allows the signal from the solid-state imaging device51to be transferred to the signal processing circuit55.

The signal processing circuit55performs a variety of types of signal processing on the signal transferred from the solid-state imaging device51. The signal having undergone the variety of signal processing (video signal) is stored in a memory of any other storage medium (not shown) or outputted to a monitor (not shown).

The above description has been made with reference to the case where the solid-state imaging device according to each of the above embodiments is used as an image sensor having unit pixels that are arranged in a matrix and detect signal charge according to the amount of visible light as a physical quantity. The solid-state imaging device described above can also be used as the entire range of column-type solid-state imaging devices having a column circuit provided for each pixel column in a pixel array section.

Further, the solid-state imaging device described above is not necessarily used as a solid-state imaging device that detects the distribution of incident visible light to capture an image but can be used as a solid-state imaging device that captures an image of the distribution of the amount of incident infrared light, X rays, particles, or any other substance. Moreover, the solid-state imaging device described above can be used as the entire range of solid-state imaging devices in a broad sense that detect the distribution of pressure, static capacitance, or any other physical quantity to capture an image (physical quantity distribution detection apparatus), such as a fingerprint detection sensor.

Further, the solid-state imaging device described above does not necessarily sequentially scan unit pixels in a pixel array section on a row basis to read a pixel signal from each of the unit pixels. For example, the solid-state imaging device described above can be used as an X-Y addressing solid-state imaging device that selects an arbitrary pixel on a pixel basis and reads a signal from the selected pixel on a pixel basis.

Moreover, the solid-state imaging device may be provided in the form of single chip or in the form of module having an imaging capability in which an imaging section and a signal processing section or an optical system are packaged together.

The technology of the present disclosure may also be implemented as the following configurations.

(1) A solid-state imaging device including a first lens layer and a second lens layer, wherein the second lens layer is formed at least at a periphery of each first microlens formed based on the first lens layer, and the second lens layer present at a central portion of each of the first microlenses is thinner than the second lens layer present at the periphery of the first microlens or no second lens layer is present at the central portion of each of the first microlenses.

(2) The solid-state imaging device described in (1), wherein the first lens layer is made of a metal-oxide-containing resin or an inorganic material, and the second lens layer is made of an inorganic material.

(3) The solid-state imaging device described in (1) or (2), wherein the first lens layer has an refractive index n1, the second lens layer has an refractive index n2, and n2≦n1is satisfied.

(4) The solid-state imaging device described in any of (1) to (3), further including a third lens layer that covers the first lens layer and the second lens layer, and the refractive index of the third lens layer is lower than the refractive indices of the first lens layer and the second lens layer.

(5) The solid-state imaging device described in (4), wherein a surface of the third lens layer is planarized.

(6) The solid-state imaging device described in any of (1) to (5), wherein the second lens layer formed at the central portion of each of the first microlenses has a thickness Tt, the second lens layer formed at the periphery of the first microlens has a thickness Tb, and 0≦Tt<Tb is satisfied.

(7) A method for manufacturing a solid-state imaging device including a first lens layer and a second lens layer, the method including forming first microlenses having an inter-pixel gap therebetween based on the first lens layer, and forming the second lens layer at least at a periphery of each of the first microlenses, wherein in the formation of the second lens layer, the second lens layer formed at a central portion of each of the first microlenses is thinner than the second lens layer formed at the periphery of the first microlens or no second lens layer is present at the central portion of each of the first microlenses.

(8) An electronic apparatus including the solid-state imaging device described in any of (1) to (6) and a signal processing circuit that processes an output signal from the solid-state imaging device.

The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2011-217423 filed in the Japan Patent Office on Sep. 30, 2011, the entire contents of which are hereby incorporated by reference.