Solid state imaging device, method of manufacturing solid-state imaging device, and electronic apparatus

The present technique aims to provide a solid-state imaging device that reduces shading and color mixing between pixels. The present invention also provides a method of manufacturing the solid-state imaging device. The present technique further relates to a solid-state imaging device that enables provision of an electronic apparatus that uses the solid-state imaging device, a method of manufacturing the solid-state imaging device, and an electronic apparatus.The solid-state imaging device includes a substrate, pixels each including a photoelectric conversion unit formed in the substrate, and a color filter layer formed on the light incidence surface side of the substrate. The solid-state imaging device also includes a device isolating portion that is formed to divide the color filter layer and the substrate for the respective pixels, and has a lower refractive index than the refractive indexes of the color filter layer and the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. 371 and claims the benefit of PCT Application No. PCT/JP2013/069509 having an international filing date of Jul. 18, 2013, which designated the United States, which PCT application claimed the benefit of Japanese Patent Application No. 2012-168365 filed Jul. 30, 2012, the disclosures of both the above-identified applications are incorporated herein by reference.

TECHNICAL FIELD

The present technique relates to solid-state imaging devices, methods of manufacturing solid-state imaging devices, and electronic apparatuses, and more particularly, to a solid-state imaging device of a back-illuminated type, a method of manufacturing the solid-state imaging device, and an electronic apparatus using the solid-state imaging device.

BACKGROUND ART

In a conventional solid-state imaging device, light-gathering on-chip lenses corresponding to respective pixels are provided on the light receiving surface side of a substrate. Light that is gathered by the on-chip lenses enters the light receiving units of the respective pixels formed in the substrate, and signal charges in accordance with the amounts of light are generated at the light receiving units.

The tilt of a principal ray that enters the solid-state imaging device via an imaging optical system provided in an imaging apparatus or the like becomes greater in the periphery of the pixel region. Therefore, at the pixels in the periphery of the pixel region formed in the solid-state imaging device, light gathered by the corresponding on-chip lenses does not enter the central portions of the light receiving units.

To counter this problem, Patent Document 1 discloses a technique by which the pitch of the on-chip lenses corresponding to the light receiving units of the respective pixels becomes narrower toward the periphery of the pixel region, compared with the pitch of the light receiving units. With this arrangement, shading correction is performed. As the pitch of the on-chip lenses is made to differ between the central region of the pixel region and the periphery of the pixel region, light that enters obliquely can be gathered into the central portion of each light receiving unit in the periphery of the pixel region.

Meanwhile, so as to improve photoelectric conversion efficiency and sensitivity to incident light, a solid-state imaging device of a so-called back-illuminated type has been recently suggested. In a solid-state imaging device of a back-illuminated type, a drive circuit is formed on the surface side of a semiconductor substrate, and the back surface of the semiconductor substrate serves as the light receiving surface. As an interconnect layer is provided on the opposite side of the substrate from the light receiving surface in the solid-state imaging device of the back-illuminated type, the distance between the light receiving units formed in the substrate and the surfaces of the on-chip lenses provided on the light incidence side of the substrate becomes shorter, and accordingly, sensitivity is increased.

Patent Document 2 discloses a solid-state imaging device of a back-illuminated type in which a trench is formed to a predetermined depth from the light receiving surface (back surface) of the substrate so as to reduce color mixing, and photodiode regions are isolated from one another by burying an insulating material in the trench. As the respective photodiode regions are isolated from one another by the insulating material buried in the trench, electrons generated in a photodiode region do not leak into an adjacent photodiode region, and color mixing can be reduced.

CITATION LIST

Patent Document

Patent Document 1: JP 01-213079 A

Patent Document 2: JP 2010-225818 A

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In a solid-state imaging device of a back-illuminated type, color filters are normally formed on the light receiving surface side of the substrate, and on-chip lenses are formed on the color filters, as in a solid-state imaging device of a front-illuminated type. In a solid-state imaging device of a back-illuminated type, the distance from the surfaces of the on-chip lenses to the light receiving surface of the substrate is shorter than that in a solid-state imaging device of a front-illuminated type, and accordingly, sensitivity is increased as described above. However, in the periphery of the pixel region in a solid-state imaging device of a back-illuminated type, shading due to oblique incident light might occur, or color mixing might be caused due to oblique light entering an adjacent pixel between color filters.

In view of the above aspects, the present disclosure aims to provide a solid-state imaging device that reduces shading and color mixing between pixels. The present disclosure also aims to provide a method of manufacturing the solid-state imaging device, and an electronic apparatus using the solid-state imaging device.

Solutions to Problems

A solid-state imaging device of the present disclosure includes a substrate, pixels each including a photoelectric conversion unit formed in the substrate, and a color filter layer formed on the light incidence surface side of the substrate. The solid-state imaging device of the present disclosure also includes a device isolating portion that is formed to divide the color filter layer and the substrate for the respective pixels, and has a lower refractive index than the refractive indexes of the color filter layer and the substrate.

As the device isolating portion is formed in the color filter layer and the substrate in the solid-state imaging device of the present disclosure, adjacent pixels are optically and electrically isolated from one another. As the device isolating portion is designed to have a lower refractive index than the refractive indexes of the color filter layer and the substrate, oblique light is prevented from entering an adjacent pixel, and light that enters the device isolating portion is gathered into the photoelectric conversion units of the respective pixels.

A method of manufacturing a solid-state imaging device of the present disclosure includes: the step of forming photoelectric conversion units in a substrate, the photoelectric conversion units corresponding to respective pixels; and the step of forming a color filter layer on the light incidence surface side of the substrate. The method of manufacturing a solid-state imaging device of the present disclosure also includes the step of forming a device isolating portion in the region to divide the color filter layer and the substrate for the respective pixels, the device isolating portion having a lower refractive index than the refractive indexes of the color filter layer and the substrate, the device isolating portion being formed prior to or after the formation of the color filter layer.

By the method of manufacturing the solid-state imaging device of the present disclosure, the device isolating portion that isolates the respective pixels from one another is formed in the color filter layer and the substrate. Accordingly, adjacent pixels are optically and electrically isolated from one another. The device isolating portion is designed to have a lower refractive index than the refractive indexes of the color filter layer and the substrate. Accordingly, oblique light is prevented from entering an adjacent pixel.

An electronic apparatus of the present disclosure includes the above described solid-state imaging device and a signal processing circuit that processes an output signal that is output from the solid-state imaging device.

Effects of the Invention

According to the present disclosure, a solid-state imaging device that reduces shading and color mixing between adjacent pixels is obtained. With the use of this solid-state imaging device, an electronic apparatus with improved image quality can be obtained.

MODES FOR CARRYING OUT THE INVENTION

The following is a description of solid-state imaging devices according to embodiments of the present disclosure, methods of manufacturing the solid-state imaging devices, and an example of an electronic apparatus, with reference toFIGS. 1 through 16. Embodiments of the present disclosure will be explained in the following order. However, the present disclosure is not limited to the examples described below.

1. First embodiment: a solid-state imaging device

1-1. Structure of the entire solid-state imaging device

1-2. Structures of main components

1-3. Manufacturing method

2. Second embodiment: an example where a pixel isolating portion is provided on a substrate

3. Third embodiment: a (first) example where a device isolating portion is hollow

3-1. Structures of main components

3-2. Manufacturing method

4. Fourth embodiment: a (second) example where a device isolating portion is hollow

5. Fifth embodiment: an example where the color filter layers are made thicker

6. Sixth embodiment: an example where a light scattering structure is provided

7. Seventh embodiment: an example where a light absorbing portion is provided

8. Eighth embodiment: a (first) example where high-refractive material portions are provided

9. Ninth embodiment: a (second) example where high-refractive material portions are provided

10. Tenth embodiment: an example where on-chip lenses are provided

11. Eleventh embodiment: an electronic apparatus

1. First Embodiment

Solid-State Imaging Device

[1-1. Structure of the Entire Solid-State Imaging Device]

First, a solid-state imaging device according to a first embodiment of the present disclosure is described.FIG. 1is a schematic view of the entire structure of a CMOS solid-state imaging device according to the first embodiment of the present disclosure.

The solid-state imaging device1of this embodiment is designed to include a pixel region3formed with pixels2arranged on a substrate11made of silicon, a vertical drive circuit4, column signal processing circuits5, a horizontal drive circuit6, an output circuit7, and a control circuit8.

As will be described later, the pixels2are designed to include photoelectric conversion units formed with photodiodes, and pixel transistors, and are regularly arranged in a two-dimensional array in the substrate11. The pixel transistors forming the pixels2may be transfer transistors, reset transistors, select transistors, and amplifying transistors, for example.

The pixel region3is formed with the pixels2regularly arranged in a two-dimensional array. The pixel region3includes an effective pixel region that actually receives light, amplifies signal charges generated through photoelectric conversion, and reads out the signal charges to the column signal processing circuits5, and a black reference pixel region (not shown) for outputting optical black that serves as the reference for black levels. The black reference pixel region is normally formed in the outer periphery of the effective pixel region.

Based on a vertical synchronization signal, a horizontal synchronization signal, and a master clock, the control circuit8generates a clock signal, a control signal, and the like that serve as the references for operation of the vertical drive circuit4, the column signal processing circuits5, the horizontal drive circuit6, and the like. The clock signal, the control signal, and the like generated by the control circuit8are input to the vertical drive circuit4, the column signal processing circuits5, the horizontal drive circuit6, and the like.

The vertical drive circuit4is formed with a shift register, for example, and selectively scans the respective pixels2in the pixel region3sequentially in the vertical direction by the row. Pixel signals that are based on the signal charges generated in accordance with the amounts of light received by the photodiodes of the respective pixels2are then supplied to the column signal processing circuits5through vertical signal lines9.

The column signal processing circuits5are provided for the respective columns of the pixels2, for example, and each of the column signal processing circuits5performs signal processing such as denoising and signal amplification through correlated double sampling to calculate a difference between a reset level and a signal level in each corresponding pixel column, on the signal output from the pixels2of each corresponding row. Horizontal select switches (not shown) are provided between the output stages of the column signal processing circuits5and a horizontal signal line10.

The horizontal drive circuit6is formed with a shift register, for example, sequentially selects the respective column signal processing circuits5by sequentially outputting horizontal scan pulses, and causes the respective column signal processing circuits5to output pixel signals to the horizontal signal line10.

The output circuit7performs signal processing on signals sequentially supplied from the respective column signal processing circuits5through the horizontal signal line10, and outputs the processed signals.

[1-2. Structures of Main Components]

FIG. 2shows the structure of the pixel region3of the solid-state imaging device1of this embodiment in cross-section. The solid-state imaging device1of this embodiment is a CMOS solid-state imaging device of a back-illuminated type, for example. In the description below, a first conductivity type is the n-type, and a second conductivity type is the p-type.

As shown inFIG. 2, the solid-state imaging device1of this embodiment includes a substrate12that includes photoelectric conversion units16provided for the respective pixels2and pixel transistors Tr, and an interconnect layer20provided on the surface side of the substrate12. The solid-state imaging device1of this embodiment also includes a spectral unit (hereinafter referred to as color filter layers23) provided on the back surface side of the substrate12. The solid-state imaging device1of this embodiment further includes a device isolating portion27that isolates the pixels2from one another.

The substrate12is formed with a semiconductor substrate made of silicon, and has a thickness of 1 to 6 μm, for example. The substrate12is formed with a semiconductor substrate of the first conductive type or the n-type, for example, and well regions13formed with impurity regions of the second conductivity type or the p-type, for example, are formed in the surface region of the substrate12on which the pixel transistors Tr are formed. In this p-type well regions13, n-type source/drain regions17forming the respective pixel transistors Tr are formed. The pixels2provided in the pixel region3are arranged in a two-dimensional matrix fashion, and each two adjacent photoelectric conversion units16are electrically isolated from each other by the device isolating portion27. Although not shown inFIG. 2, a peripheral circuit unit is formed in the peripheral region of the pixel region3.

The photoelectric conversion units16are provided for the respective pixels2in one-to-one correspondence. The photoelectric conversion units16are formed with p-type semiconductor regions15formed on the surface side of the substrate12, and n-type semiconductor regions14provided from the depth of the back surface of the substrate12to the depth of the p-type semiconductor regions15. In each of the photoelectric conversion units16, the principal portion of the photodiode is formed with the pn junction between the p-type semiconductor region15and the n-type semiconductor region14.

In each of these photoelectric conversion units16, signal charges in accordance with amounts of incident light are generated, and are accumulated in the n-type semiconductor region14. As the p-type semiconductor regions15are provided in the surface of the substrate12, generation of dark current in the surface of the substrate12is restrained.

Each of the pixel transistors Tr is formed with a source/drain region17provided on the surface side of the substrate12, and a gate electrode22provided on the surface of the substrate12via a gate insulating film not shown in the drawing. Each of the source/drain regions17is formed with a high-density n-type semiconductor region provided in the corresponding well region13, and is formed by ion implantation of an n-type impurity from the surface of the substrate12.

The gate electrodes22are made of polysilicon, for example. Transfer transistors, amplifying transistors, reset transistors, select transistors, and the like are formed as the pixel transistors Tr that drive the pixels2, butFIG. 2shows only the transfer transistors as the pixel transistors Tr. Accordingly, the source/drain regions17shown inFIG. 2are equivalent to the drain regions that are the floating diffusion regions forming the transfer transistors.

The color filter layers23are made of an organic material, for example, and are provided on the back surface side of the substrate12via a back-surface-side fixed charge film28having negative fixed charges described later and back-surface-side insulating films38. The material of the back-surface-side fixed charge film28will be described later. The back-surface-side insulating films38can be made of a material with a lower refractive index than the color filter layers23and the substrate12, and be made of SiO2, SIN, or the like.

The color filter layers23are provided for the respective photoelectric conversion units16, and a filter layer that selectively passes light of R (red), G (green), or B (blue) is provided for each pixel2. Light of a desired wavelength is transmitted through the color filter layers23, and the transmitted light enters the photoelectric conversion units16in the substrate12.

The device isolating portion27is formed with a groove portion24formed to extend from the surfaces of the color filter layers23to a predetermined depth in the substrate12, and a negative-fixed-charge-containing film (hereinafter referred to as the in-groove fixed charge film26) and an insulating film25that are buried in the groove portion24in this order. The device isolating portion27is formed in a grid-like pattern, and is designed to isolate the pixels2from one another.

The groove portion24is formed to extend from the surfaces of the color filter layers23to the well regions13in which the source/drain regions17of the pixel transistors Tr in the substrate12are formed, but not to reach the source/drain regions17.

The in-groove fixed charge film26is formed to cover the inner wall surfaces of the groove portion24on the side of the substrate12. In this embodiment, the back-surface-side fixed charge film28and the in-groove fixed charge film26are formed with an insulating film containing fixed charges (negative fixed charges in this embodiment) of the same polarity as the signal charges stored in the photoelectric conversion units16. Further, in this embodiment, the in-groove fixed charge film26forming the device isolating portion27is made of a material with a lower refractive index than the materials forming the substrate12and the color filter layers23.

The insulating film containing negative fixed charges may be a hafnium oxide (HfO2) film, an aluminum oxide (Al2O3) film, a zirconium oxide (ZrO2) film, a tantalum oxide (Ta2O5) film, or a titanium oxide (TiO2) film, for example. Examples of methods of forming this insulating film include a chemical vapor deposition technique (CVD technique), a sputtering technique, an atomic layer deposition technique (ALD technique), and the like. By using an atomic layer deposition method, a SiO2film that is approximately 1 nm and reduces interface states during film formation can be formed at the same time. Examples of materials other than the above include lanthanum oxide (La2O3), praseodymium oxide (Pr2O3), cerium oxide (CeO2), neodymium oxide (Nd2O3), promethium oxide (Pm2O3), and the like. Examples of such materials further include samarium oxide (Sm2O3), europium oxide (Eu2O3), gadolinium oxide (Gd2O3), terbium oxide (Tb2O3), dysprosium oxide (Dy2O3), and the like. Examples of such materials further include holmium oxide (Ho2O3), thulium oxide (Tm2O3), ytterbium oxide (Yb2O3), lutetium oxide (Lu2O3), yttrium oxide (Y2O3), and the like. Further, the above insulating film containing negative fixed charges may be formed with a hafnium nitride film, an aluminum nitride film, a hafnium oxynitride film, or an aluminum oxynitride film.

Silicon (Si) or nitrogen (N) may be added to the insulating film containing negative fixed charges, without degrading insulation properties. The density of the silicon or nitrogen to be added is determined so as not to degrade the insulation properties of the film. As silicon (Si) or nitrogen (N) is added to the insulating film in this manner, the heat-resisting properties of the insulating film and the ion implantation blocking capability during a process can be improved.

Of the above mentioned insulating films containing negative fixed charges, an insulating film with a lower refractive index than the material forming the substrate12can form the in-groove fixed charge film26. The material of the in-groove fixed charge film26may be HfO2or Ta2O5, for example.

As the insulating films containing negative fixed charges (the in-groove fixed charge film26and the back-surface-side fixed charge film28) are formed on the inner wall surfaces of the groove portion24and the back surface of the substrate12in this embodiment, an inversion layer is formed on the surface in contact with those insulating films containing negative fixed charges. With this, an inversion layer with charges (holes in this embodiment) of the opposite polarity of the signal charges is formed on the inner wall surfaces of the groove portion24formed in the substrate12and on the back surface of the substrate12, and this inversion layer restrains generation of dark current.

The insulating film25is formed to fill the groove portion24coated with the in-groove fixed charge film26. The insulating film25is made of an insulating material having a lower refractive index than the materials forming the substrate12and the color filter layers23and the fixed charge films, and may be formed with SiO2, SiN, or the like.

Although the groove portion24is filled with the insulating film25in this embodiment, the in-groove fixed charge film26may be designed to be thick, and the groove portion24may be filled only with the in-groove fixed charge film26. In this case, the in-groove fixed charge film should be made of a material having a lower refractive index than the refractive index of the color filter layers23. Alternatively, the in-groove fixed charge film26may fill only the groove portion24formed in the substrate12, and the groove portion24between the color filter layers23may not be filled with anything.

The interconnect layer20is formed on the surface side of the substrate12, and is designed to include interconnects19(four layers in this embodiment), with an interlayer insulating film18being interposed between these interconnects19. Also, the interconnects19located on one another, and the interconnects19and the pixel transistors Tr are connected via connection vias21formed in the interlayer insulating film18as necessary.

In the solid-state imaging device1having the above described structure, the back surface side of the substrate12is illuminated with light, and the light transmitted through the color filter layers23is photoelectrically converted by the photoelectric conversion units16. In this manner, signal charges are generated. The signal charges generated by the photoelectric conversion units16are then output as pixel signals from vertical signal lines (not shown) formed with the predetermined interconnects19in the interconnect layer20, via the pixel transistors Tr formed on the surface side of the substrate12.

In this embodiment, the refractive indexes of the in-groove fixed charge film26and the insulating film25formed in the groove portion24are lower than the refractive indexes of the substrate12and the color filter layers23. Accordingly, in the solid-state imaging device1of this embodiment, a light collecting tube structure is formed, with the core being the color filter layers23and the photoelectric conversion units16formed in the substrate12, the cladding being the device isolating portion27.

With this arrangement in the solid-state imaging device1of this embodiment, light that enters the device isolating portion27is absorbed by the color filter layers23and the substrate12having higher refractive indexes than that of the device isolating portion27. Meanwhile, in the light incidence surface, light that enters the color filter layers23does not enter the device isolating portion27. Therefore, light that obliquely enters a predetermined color filter layer23does not enter the color filter layer23of an adjacent pixel2.

Furthermore, in the solid-state imaging device1of this embodiment, the photoelectric conversion units16are electrically isolated from one another by the device isolating portion27in the substrate12. Accordingly, the signal charges generated by a photoelectric conversion unit16do not leak into the photoelectric conversion unit16of an adjacent pixel2. Accordingly, color mixing can be restrained.

As described above, the device isolating portion27formed in this embodiment functions to optically isolate the pixels2from one another among the color filter layers23, and electrically isolate the pixels2from one another among the photoelectric conversion units16.

Also, in the device isolating portion27, an insulating portion such as the insulating film25buried in the groove portion24is preferably designed to be level with the surfaces of the color filter layers23in the light incidence surface or protrude from the surfaces (the light incidence surfaces) of the color filter layers23. As the device isolating portion27prevents the color filter layers23from connecting to each other between adjacent pixels2, optical isolation among the color filter layers23can be secured.

Also, in the solid-state imaging device1of this embodiment, light can be divided by the respective pixels2on the incidence surface boundary of the solid-state imaging device1. Accordingly, light collection by semi-spherical on-chip lenses that are used in conventional solid-state imaging devices is unnecessary. In a case where a conventional solid-state imaging device is incorporated into an imaging apparatus such as a camera, the optimum positions of on-chip lenses, color filter layers, and photoelectric conversion units need to be corrected in accordance with the characteristics of an optical system that is set for forming images on the solid-state imaging device.

In this embodiment, on the other hand, light can be divided by the pixels2on the incidence surface boundary of the solid-state imaging device1. Therefore, the above correction, or pupil correction, is unnecessary. Accordingly, there is no need to change the design of the solid-state imaging device1in accordance with an optical system set in an imaging apparatus in this embodiment. Also, with the use of the solid-state imaging device1of this embodiment, the compatible range becomes wider and a higher degree of freedom is allowed for lenses in the case of an interchangeable lens imaging apparatus or in a case where the eye pupil distance varies with the focal lengths of zoom lenses.

Next, a method of manufacturing the solid-state imaging device1of this embodiment is described.FIGS. 3A through 4Eare process charts showing the method of manufacturing the solid-state imaging device1of this embodiment.

First, as shown inFIG. 3A, after the photoelectric conversion units16and the pixel transistors Tr are formed in the substrate12, the interlayer insulating film18and the interconnects19are alternately formed on the surface of the substrate12, to form the interconnect layer20. In the process charts shown inFIGS. 3A through 4F, only the interconnect layer20near the surface of the substrate12is shown. The impurity regions such as the photoelectric conversion units16and the source/drain regions17, which are formed in the substrate12, are formed by implanting ions of a predetermined impurity from the surface side of the substrate12, for example.

A supporting substrate (not shown) formed with a silicon substrate is bonded to the uppermost layer of the interconnect layer20, and the substrate12is turned upside down. The manufacturing procedures up to this point are the same as the procedures for manufacturing a conventional solid-state imaging device of a back-illuminated type. Although not shown in the drawings, after the substrate12is turned upside down, the back surface side of the substrate12is polished to reduce the thickness of the substrate12to a desired thickness.

As shown inFIG. 3A, a fixed charge film28aand an insulating film38aare then formed on the entire back surface of the substrate12, and a hard mask29made of SiN, for example, is formed on the insulating film38a. The hard mask29is formed by forming a SiN layer on the back surface of the substrate12by low-temperature CVD, and then performing etching on the SiN layer so as to leave the SiN layer only on the photoelectric conversion units16of the respective pixels2by using a photolithography technique. In this manner, the hard mask29having an opening29aimmediately above the region in which the device isolating portion27is to be formed is completed.

As shown inFIG. 3B, the groove portion24is then formed. The groove portion24is formed by performing etching on the substrate12until the groove reaches a predetermined depth via the hard mask29or a depth at which the well regions13are located in this embodiment. At this point, the fixed charge film28aand the insulating film38aexposed through the opening29aof the hard mask29are also subjected to the etching. As a result, the back-surface-side fixed charge film28and the back-surface-side insulating film38are formed in the region corresponding to the respective photoelectric conversion units34on the back surface of the substrate12.

As shown inFIG. 3C, an in-groove fixed charge film26aand the insulating film25are then formed in this order in the groove portion24. In this stage, the in-groove fixed charge film26ais first formed by using CVD, a sputtering technique, ALD, or the like, so as to cover the inner wall surfaces of the groove portion24. The in-groove fixed charge film26aformed in this stage is to form the in-groove fixed charge film26shown inFIG. 2. After that, the insulating film25to fill the groove portion24is formed by using SOG (Spin on Glass) or CVD. In this embodiment, SiO2is used as the insulating film25.

At this point, the in-groove fixed charge film26aand the insulating film25are also formed on the surface of the hard mask29. Therefore, after the in-groove fixed charge film26aand the insulating film25are formed, the in-groove fixed charge film26aand the insulating film25formed on the hard mask surface are polished by using CMP (Chemical Mechanical Polishing) until the hard mask29is exposed. In this manner, the in-groove fixed charge film26aand the insulating film25are formed in the groove portion24as shown inFIG. 3C.

As shown inFIG. 4D, the SiN film used as the hard mask29is then removed by wet etching. In this stage, the portions of the in-groove fixed charge film26aprotruding from the back surface of the substrate12are also removed together with the hard mask29, as shown inFIG. 4D. As a result, the in-groove fixed charge film26remains only in the groove portion24formed in the substrate12. Since the back-surface-side insulating film38is formed on the back surface side of the substrate12at this point, the back-surface-side fixed charge film28is not removed.

As shown inFIG. 4E, the desired color filter layers23are then formed for the respective pixels2by using a lithography technique. In this case, the color filter layers23are formed so as to fill the concave portions formed by the substrate12, and the in-groove fixed charge film26and the insulating film25protruding from the back surface of the substrate12, as shown inFIG. 4E.

After that, the color filter layers23are polished by using CMP until the in-groove fixed charge film26formed on the surface of the insulating film25is exposed, for example. As a result, the solid-state imaging device1shown inFIG. 2is completed. Although the color filter layers23are polished until the in-groove fixed charge film26is exposed in this embodiment, the polishing may be continued until the surfaces of the color filter layers23become closer to the substrate12than the surface of the in-groove fixed charge film26is.

Although the groove portion24formed to extend from the color filter layers23to the substrate12is formed through one procedure in the solid-state imaging device1of this embodiment, the present technique is not limited to that. For example, the device isolating portion27that isolates the photoelectric conversion units16from one another in the substrate12may be formed through a different procedure from the procedure for forming the device isolating portion27that isolates the color filter layers23from one another.

In a case where the device isolating portion27in the substrate12is formed through a different procedure from the procedure for forming the device isolating portion27for the color filter layers23, however, there might be misalignment between the device isolating portions27in the boundary surfaces between the substrate12and the color filter layers23. In such a case, sensitivity loss and color mixing degradation are caused. By the method of manufacturing the solid-state imaging device1of this embodiment, the groove portion24forming the device isolating portion27is formed by one etching procedure. Accordingly, process differences (misalignment in the device isolating portion27) can be made smaller, and the number of manufacturing procedures can be made smaller, compared with those in a case where the device isolating portion27in the substrate12is formed through a different procedure from the procedure for forming the device isolating portion27for the color filter layers23.

Since the process differences can be made smaller in this embodiment, sensitivity loss and color mixing degradation can be prevented more effectively than in a case where the device isolating portion27in the substrate12is formed through a different procedure from the procedure for forming the device isolating portion27for the color filter layers23.

Although an n-type semiconductor substrate is used as the substrate12in this embodiment, a semiconductor substrate including an n-type epitaxial layer in which impurity density becomes higher toward the surface side may be used as the substrate12, for example. Other than that, a semiconductor substrate including a p-type epitaxial layer in which impurity density becomes lower toward the surface side may be used as the substrate12. As such a semiconductor substrate is used as the substrate12, electric fields can be readily formed by the transfer transistors. Accordingly, even in a case where the semiconductor layer on which the photoelectric conversion units32are formed is thick, signal charges can be prevented from failing to be transferred.

2. Second Embodiment

Example where a Pixel Isolating Portion is Provided on a Substrate

FIG. 5is a cross-sectional view of the main components of a solid-state imaging device according to a second embodiment of the present disclosure. The solid-state imaging device30of this embodiment differs from the first embodiment in that the in-groove fixed charge film and the back-surface-side fixed charge film are not formed. Therefore, inFIG. 5, the same components as those shown inFIG. 2are denoted by the same reference numerals as those used inFIG. 2, and explanation of them is not repeated herein. Also, the entire structure of the solid-state imaging device30of this embodiment is the same as the structure shown inFIG. 1, and therefore, explanation thereof will not be repeated herein.

In the solid-state imaging device30of this embodiment, each of photoelectric conversion units32is formed with high-density p-type semiconductor regions31and15formed on the back surface and the surface of the substrate12, and an n-type semiconductor region14formed between the two p-type semiconductor regions31and15. That is, in the solid-state imaging device30of this embodiment, the pn junctions of the p-type semiconductor regions31and15and the n-type semiconductor regions14form principal photodiodes.

Also, in the solid-state imaging device30of this embodiment, a pixel isolating portion34formed with a p-type semiconductor region is formed so as to isolate the photoelectric conversion units32from one another in the substrate12, as shown inFIG. 5. The pixel isolating portion34is formed to extend from the back surface of the substrate12to the depth of the well regions13in which the source/drain regions17of the pixel transistors Tr are formed, for example.

In this embodiment, a device isolating portion33is formed inside the pixel isolating portion34designed to isolate the photoelectric conversion units32from one another in the substrate12. That is, in the substrate12, the side peripheral surfaces of the device isolating portion33are covered with the p-type semiconductor region forming the pixel isolating portion34. In this embodiment, the device isolating portion33is also formed to extend to the depth of the well regions13in which the source/drain regions17of the pixel transistors Tr are formed.

The pixel isolating portion34and the p-type semiconductor regions31can be formed by implanting ions of a p-type impurity at high density from the surface of the substrate12before the interconnect layer20is formed. Alternatively, the pixel isolating portion34and the p-type semiconductor regions31may be formed by implanting ions of a p-type impurity at high density from the back surface side of the substrate12after the interconnect layer20is formed on the surface of the substrate12, the substrate12is turned upside down, and the substrate12is subjected to film thinning treatment.

In the solid-state imaging device30of this embodiment, the device isolating portion33is formed with the groove portion24formed to extend from the color filter layers23to a predetermined depth in the substrate12, and the insulating film25buried in the groove portion24. This insulating film25can be made of the same material as the insulating film25of the first embodiment. That is, in the solid-state imaging device30of this embodiment, insulating films containing negative fixed charges are not formed on the inner wall surfaces of the device isolating portion27and the back surface of the substrate12.

Since the p-type semiconductor regions31and15are formed on the back surface and the surface of the substrate12in the solid-state imaging device30of this embodiment, dark current to be generated in the interfaces of the substrate12can be reduced. Furthermore, as the groove portion24forming the device isolating portion33is surrounded by p-type semiconductor regions (the pixel isolating portion34and the well regions13), dark current to be generated in the inner wall surfaces of the groove portion24can be reduced.

As described above, in this embodiment, the groove portion24is surrounded by the p-type semiconductor regions that form the pixel isolating portion34and the well regions13, and the p-type semiconductor regions31are also formed on the back surface of the substrate12. Accordingly, in the interfaces of the substrate12, dark current can be reduced by the layers of the opposite polarity of the polarity of the signal charges to be generated by the photoelectric conversion units32, and there is no need to form insulating films that contain negative fixed charges and cover the inner wall surfaces of the groove portion24and the back surface of the substrate12in this embodiment.

Since there is no need to form insulating films containing negative fixed charges in the solid-state imaging device30of this embodiment, the procedures for forming the insulating films containing negative fixed charges can be skipped in the procedures of the first embodiment shown inFIGS. 3C and 4E. In this embodiment, the device isolating portion33is also formed to extend from the color filter layers23to a predetermined depth in the substrate12, and accordingly, the same effects as those of the first embodiment can be achieved.

In this embodiment, insulating films containing negative fixed charges may also be formed on the inner wall surfaces of the groove portion24and the back surface of the substrate12, as in the first embodiment. In such a case, the hole pinning effect of the insulating films containing negative fixed charges becomes greater, and accordingly, the dark current reducing effect also becomes greater. In a case where insulating films containing negative fixed charges are formed on the inner wall surfaces of the groove portion24and the back surface of the substrate12in this embodiment, the impurity densities in the p-type semiconductor region forming the pixel isolating portion34and the p-type semiconductor regions31forming the photoelectric conversion units32can be made lower.

Also, in this embodiment, a conductive film such as an ITO film may be buried in the groove portion24via an insulating film, and a negative potential may be applied to the conductive film. In this case, holes are generated in the inner wall surfaces of the groove portion24, and accordingly, dark current can be reduced.

(First) Example where a Device Isolating Portion is Hollow

Next, a solid-state imaging device according to a third embodiment of the present disclosure is described.FIG. 6is a cross-sectional view of the main components of the solid-state imaging device40of this embodiment. This embodiment differs from the second embodiment in that the in-groove fixed charge film and the insulating film that cover the inner wall surfaces of the groove portion24are not provided. Therefore, inFIG. 6, the same components as those shown inFIGS. 2 and 5are denoted by the same reference numerals as those used inFIGS. 2 and 5, and explanation of them is not repeated herein. Also, the entire structure of the solid-state imaging device40of this embodiment is the same as the structure shown inFIG. 1, and therefore, explanation thereof will not be repeated herein.

[3-1. Structures of Main Components]

In the solid-state imaging device40of this embodiment, the groove portion24is hollow, and the unfilled groove portion24forms a device isolating portion43. In the solid-state imaging device40of this embodiment, the groove portion24is formed in the pixel isolating portion34formed with a p-type semiconductor region, as in the second embodiment. As the groove portion24is formed in the pixel isolating portion34formed with a p-type semiconductor region, dark current to be generated in the inner wall surfaces of the groove portion24can be reduced.

Next, a method of manufacturing the solid-state imaging device40of this embodiment is described.FIGS. 7A and 7Bare process charts showing the method of manufacturing the solid-state imaging device40of this embodiment.

First, as shown inFIG. 7A, after the photoelectric conversion units16, the pixel isolating portion34, and the pixel transistors Tr are formed in the substrate12, the interlayer insulating film18and the interconnects19are alternately formed on the surface of the substrate12, to form the interconnect layer20. In the process charts shown inFIGS. 7A and 7B, only the interconnect layer20near the surface of the substrate12is shown. The impurity regions such as the photoelectric conversion units16, the pixel isolating portion34, and the source/drain regions17, which are formed in the substrate12, are formed by implanting ions of a predetermined impurity from the surface side of the substrate12.

A supporting substrate (not shown) formed with a silicon substrate is bonded to the uppermost layer of the interconnect layer20, and the substrate12is then turned upside down. The manufacturing procedures up to this point are the same as the procedures for manufacturing a conventional solid-state imaging device of a back-illuminated type. Although not shown in the drawings, after the substrate12is turned upside down, the back surface side of the substrate12is polished to reduce the thickness of the substrate12to a desired thickness. The pixel isolating portion34may be formed by implanting ions of a p-type impurity at a desired depth from the back surface side of the substrate12after the substrate12is thinned.

After that, as shown inFIG. 7A, the fixed charge film28ato be the back-surface-side fixed charge film28is formed on the back surface of the substrate12, and the color filter layers23are formed on the fixed charge film.28a. The fixed charge film28ais formed by using CVD, a sputtering technique, ALD, or the like. The color filter layers23are formed for the respective pixels by using a lithography technique. Since the procedure for removing the fixed charge film between the color filter layers23as shown inFIG. 4Dis not carried out in this embodiment, the back-surface-side insulating film38shown inFIG. 4Dis unnecessary.

As shown inFIG. 7B, a hard mask44formed with an inorganic film that has an opening portion44aimmediately above the region to form the groove portion24is then formed over the color filter layers23. The hard mask44is formed by forming a SiN layer over the color filter layers23, and then performing etching so as to leave the SiN layer on the photoelectric conversion units16of the respective pixels2by using a photolithography technique.

Etching is then performed via the hard mask44, to form the groove portion24. The groove portion24is formed by performing etching on the substrate12until the groove reaches a predetermined depth via the hard mask44or a depth at which the well regions13are located in this embodiment. At this point, the fixed charge film28aexposed through the opening29aof the hardmask29is also subjected to the etching. As a result, the back-surface-side fixed charge film28is formed in the region corresponding to the respective photoelectric conversion units34on the back surface of the substrate12. After that, the hard mask44is removed, and the solid-state imaging device40of this embodiment shown inFIG. 6is completed.

Although not shown in the drawings, a passivation film may be formed so as to cover the inner wall surfaces of the groove portion24and the surfaces of the color filter layers23, as necessary. The passivation film can be formed by using low-temperature CVD, for example.

In the solid-state imaging device40of this embodiment, the device isolating portion43is formed with the hollow groove portion24. Therefore, at the time of packaging, this hollow groove portion24is filled with air. Air has a lower refractive index than the color filter layers23made of an organic material and the substrate12made of silicon. Accordingly, in this embodiment, a light collecting tube structure is formed as in the first embodiment, with the core being the photoelectric conversion units16and the color filter layers23, the cladding being the groove portion24(the device isolating portion43).

Therefore, light that obliquely enters the surface of a predetermined color filter layer23does not enter the color filter layer23of an adjacent pixel2among the color filter layers23. Furthermore, the signal charges generated by a photoelectric conversion unit16in the substrate12do not leak into the photoelectric conversion unit16of an adjacent pixel2. As described above, the device isolating portion43formed in this embodiment functions to optically isolate the pixels2from one another among the color filter layers23, and electrically isolate the pixels2from one another among the photoelectric conversion units16, as in the first embodiment.

As there is no need to bury a fixed charge film in the groove portion24in the solid-state imaging device40of this embodiment, the number of procedures can be reduced. Although the SiO2layer formed as the hard mask44is removed in this embodiment, the hard mask44can remain as a low reflecting coating when the material and the thickness of the inorganic film forming the hard mask44are appropriately selected. In this case, the inorganic film used as the hard mask44may be made of a single material, or may be formed with a film stack of films made of different materials, such as a film stack of a SiO2film and a SiN film.

Next, another example of the method of manufacturing the above described solid-state imaging device40according to the third embodiment is described as a modification.FIG. 8is a diagram showing one procedure in the method of manufacturing the solid-state imaging device40according to the modification.

In the modification, the procedures up to the formation of a fixed charge film on the back surface of the substrate12are the same as those of the third embodiment, and the procedure for forming the groove portion24differs from that of the third embodiment. Therefore, explanation of the procedures up to the formation of the back-surface-side fixed charge film28on the back surface of the substrate12is not repeated herein.

As shown inFIG. 8, in the modification, the fixed charge film28ato be the back-surface-side fixed charge film28is formed on the back surface of the substrate12, and the color filter layers23having an opening23aimmediately above the region forming the groove portion24are then formed by using a photolithography technique. In this manner, the color filter layers23are formed at a distance from one pixel to another. As the color filter layers23formed as shown inFIG. 8serve as a mask, etching is performed on the back-surface-side fixed charge film.28and the substrate12, to complete the solid-state imaging device40shown in FIG.6.

As described above, the number of procedures can be reduced by using the color filter layers23as a mask and forming the groove portion24after the patterning of the color filter layers23is performed.

(Second) Example where a Device Isolating Portion is Hollow

Next, a solid-state imaging device according to a fourth embodiment of the present disclosure is described.FIG. 9is a cross-sectional view of the main components of the solid-state imaging device50of this embodiment. The solid-state imaging device50of this embodiment differs from the solid-state imaging device40according to the third embodiment in that the pixel isolating portion is not formed, and an in-groove fixed charge film51to cover the inner wall surfaces of the groove portion24is provided. Therefore, inFIG. 9, the same components as those shown inFIGS. 2 and 6are denoted by the same reference numerals as those used inFIGS. 2 and 6, and explanation of them is not repeated herein. Also, the entire structure of the solid-state imaging device50of this embodiment is the same as the structure shown inFIG. 1, and therefore, explanation thereof will not be repeated herein.

In the solid-state imaging device50of this embodiment, a device isolating portion52is formed with the groove portion24formed to extend from the surfaces of the color filter layers23to the well regions13in the substrate12, and an in-groove fixed charge film51provided to cover the groove portion24. In this embodiment, the in-groove fixed charge film51is also formed on the surfaces of the color filter layers23.

This in-groove fixed charge film51is formed so as to cover the inner wall surfaces of the groove portion24and the surfaces of the color filter layers23after the groove portion24is formed in the same manner as inFIG. 7B. In this embodiment, the in-groove fixed charge film51is made of a material that has a lower refractive index than the refractive index of the color filter layers23and contains negative fixed charges.

In the solid-state imaging device50of this embodiment, a pixel isolating portion formed with a p-type semiconductor region is not formed in the substrate12, but the inner wall surfaces of the groove portion24are covered with the in-groove fixed charge film51. Accordingly, dark current generation in the interfaces of the groove portion24can be restrained.

Although the pixel isolating portion formed with a p-type semiconductor region is not provided in the substrate12in this embodiment, the pixel isolating portion may be formed, and the groove portion24may be formed in the pixel isolating portion as in the third embodiment. In such a case, the hole pinning effect of the in-groove fixed charge film51is increased, and generation of dark current can be more effectively restrained. In addition to the above effects, this embodiment can achieve the same effects as those of the first through third embodiments.

Example where the Color Filter Layers are Made Thicker

Next, a solid-state imaging device according to a fifth embodiment of the present disclosure is described.FIG. 10is a cross-sectional view of the main components of the solid-state imaging device60of this embodiment. The solid-state imaging device60of this embodiment differs from the first embodiment in the structures of color filter layers61. Therefore, inFIG. 10, the same components as those shown inFIG. 2are denoted by the same reference numerals as those used inFIG. 2, and explanation of them is not repeated herein. Also, the entire structure of the solid-state imaging device60of this embodiment is the same as the structure shown inFIG. 1, and therefore, explanation thereof will not be repeated herein.

In this embodiment, the thickness of the color filter layers61is greater than the thickness of the color filter layers23of the solid-state imaging device1according to the first embodiment, and is 1 μm or greater. While the thickness of the color filter layers is approximately 500 nm in a conventional solid-state imaging device, the color filter layers61in the solid-state imaging device60of this embodiment has a thickness of 1 μm or greater, which is much greater than that in a conventional solid-state imaging device.

The pigment concentration in the color filter layers61may be substantially the same as the pigment concentration in the color filter layers23in the first embodiment, or may be lower than the pigment concentration in the color filter layers23in the first embodiment. As the pigment concentration in the color filter layers61is adjusted in this manner, spectral sensitivity can also be adjusted in this embodiment.

In this embodiment, the device isolating portion27is formed to extend from the surfaces of the color filter layers61to the depth at which the well region13are formed in the substrate12, as in the first embodiment.

The solid-state imaging device60of this embodiment can be manufactured by adjusting the thickness of the hard mask29to 1 μm or greater in the procedure shown inFIG. 3Ain the first embodiment, for example. In the solid-state imaging device60of this embodiment, the pixels2are also isolated from one another by the device isolating portion27in the region extending from the color filter layers61to the substrate12. Accordingly, in the solid-state imaging device60of this embodiment, a light collecting tube structure is formed, with the core being the color filter layers61and the photoelectric conversion units16formed in the substrate12, the cladding being the device isolating portion27.

In the solid-state imaging device60of this embodiment, the color filter layers61are made thicker, so that light that enters the device isolating portion27in the light incidence surface is sufficiently absorbed by the color filter layers61forming the core, and then enters the photoelectric conversion units16. Accordingly, spectral characteristics are improved in the solid-state imaging device60of this embodiment. With the solid-state imaging device60of this embodiment, the same effects as those of the first embodiment can also be achieved.

Example where a Light Scattering Structure is Provided

Next, a solid-state imaging device according to a sixth embodiment of the present disclosure is described.FIG. 11is a cross-sectional view of the main components of the solid-state imaging device70of this embodiment. The solid-state imaging device70of this embodiment differs from the solid-state imaging device1of the first embodiment in that a corrugated surface71is formed in the back surface of the substrate12serving as the light incidence surface. Therefore, inFIG. 11, the same components as those shown inFIG. 2are denoted by the same reference numerals as those used inFIG. 2, and explanation of them is not repeated herein.

In the solid-state imaging device70of this embodiment, the back surface of the substrate12serving as the light incidence surface is processed to have minute concavities and convexities as shown inFIG. 11, so that the corrugated surface71is formed in the back surface of the substrate12. The corrugated surface71formed in the back surface of the substrate12is also designed to have such a shape as to increase the incidence angle of incident light. This corrugated surface71forms a light scattering structure between the substrate12and the color filter layers23.

In the solid-state imaging device70of this embodiment, after the interconnect layer20is formed on the surface of the substrate12, a supporting substrate is bonded to the surface of the interconnect layer20on the side of the substrate12, and the substrate12is turned upside down. The corrugated surface71is then formed while the substrate12is subjected to film thinning treatment. When the substrate12is subjected to film thinning treatment, the back surface of the substrate12is polished to a predetermined depth by CMP, for example. At this point, with the use of a predetermined abrasive, rough polishing is performed in the film thinning treatment. As a result, the corrugated surface71can be formed in the back surface of the substrate12, as shown inFIG. 11.

As the light incidence surface of the substrate12is the corrugated surface71in the solid-state imaging device70of this embodiment, the incidence angle of incident light becomes greater. In a case where the corrugated surface71is designed so that light entering perpendicularly to the light incidence surface of the substrate12is bent 45 degrees, for example, the optical path length in the photoelectric conversion units16is 1.4 times the optical path length formed in a case where light enters perpendicularly. As the incidence angle of incident light is changed in this manner, the optical path length in the photoelectric conversion units16can be increased, and particularly, the sensitivity to long-wavelength light (such as red) can be improved. In addition to the above effects, the same effects as those of the first embodiment can also be achieved with the solid-state imaging device70of this embodiment.

Although the back surface of the substrate12is the corrugated surface71in the solid-state imaging device70of this embodiment, the light incidence surfaces of the color filter layers23may be corrugated surfaces, and the same effects as those of this embodiment can be achieved if alight scattering structure is formed on the light incidence side of the photoelectric conversion units16.

As the surface located between the photoelectric conversion units16and the color filter layers23is the corrugated surface71in this embodiment, the incidence angle of incident light that has passed through the color filter layers23is increased by the corrugated surface71before entering the photoelectric conversion units16. Accordingly, only the optical path after light enters the photoelectric conversion units16can be made longer, without a change in the spectral path of incident light in the color filter layers23.

The above described corrugated surface71effectively increases the optical path length in the photoelectric conversion units16in a case where long-wavelength light is photoelectrically converted. Therefore, the corrugated surface71may be provided only for the red pixels2, but the corrugated surface71may not be provided for the green and blue pixels.

Example where a Light Absorbing Portion is Provided

Next, a solid-state imaging device according to a seventh embodiment of the present disclosure is described.FIG. 12is a cross-sectional view of the main components of the solid-state imaging device80of this embodiment. The solid-state imaging device80of this embodiment differs from the solid-state imaging device1of the first embodiment in the structure of a device isolating portion82and a light absorbing portion83formed on the device isolating portion82. Therefore, inFIG. 12, the same components as those shown inFIG. 2are denoted by the same reference numerals as those used inFIG. 2, and explanation of them is not repeated herein. Also, the entire structure of the solid-state imaging device80of this embodiment is the same as the structure shown inFIG. 1, and therefore, explanation thereof will not be repeated herein.

In the solid-state imaging device80of this embodiment, the device isolating portion82is formed with the groove portion24, and the in-groove fixed charge film26, the insulating film25, and a nontransparent film81, which are buried in this order in the groove portion24. The in-groove fixed charge film26is formed so as to cover the inner wall surfaces of the groove portion24on the side of the substrate12, and the insulating film25is formed in the groove portion24so as to cover the in-groove fixed charge film26. The insulating film25is designed to have such a thickness as not to fill the entire groove portion24. The nontransparent film81is formed so as to fill the groove portion24having the in-groove fixed charge film26and the insulating film25formed therein.

The in-groove fixed charge film26and the insulating film25can be made of the same material as those of the first embodiment. The nontransparent film81can be made of an optically nontransparent metal material such as Al or W.

The device isolating portion82can be formed by forming the in-groove fixed charge film26and the insulating film25, etching a middle region in the insulating film25, and filling the formed groove with a desired metal material, as in the procedures in the first embodiment shown inFIGS. 3A through 4E.

The light absorbing portion83is formed on the device isolating portion82, and is made of polysilicon or a light absorbing material such as a chalcopyrite-based material.

This light absorbing portion83can be formed by forming a light absorbing material layer on the entire surface including the device isolating portion82after the formation of the device isolating portion82, and performing etching by a photolithography technique in such a manner that the light absorbing material layer remains only on the device isolating portion82. After the light absorbing portion83made of a light absorbing material is formed on the device isolating portion82, the color filter layers23are formed in the same manner as in the procedure shown inFIG. 4F, and the solid-state imaging device80of this embodiment is completed.

In this embodiment, the light incidence surfaces of the color filter layers23are substantially level with the surface of the light absorbing portion83, or are closer to the substrate12than the surface of the light absorbing portion83is.

As the light absorbing portion83is formed on the light incidence surface side of the device isolating portion82in the solid-state imaging device80of this embodiment, the amount of light that enters the device isolating portion82can be reduced. Accordingly, the spectral characteristics in the color filter layers23can be improved.

Furthermore, in the solid-state imaging device80of this embodiment, the nontransparent film81made of a metal material is provided in the groove portion24in the device isolating portion82. With this arrangement, the spectral characteristics between adjacent pixels2can be further improved, and color mixing can be further reduced accordingly. In addition to the above effects, this embodiment can achieve the same effects as those of the first embodiment.

In the solid-state imaging device80of this embodiment, a predetermined potential may be applied to the nontransparent film81made of a metal material. As a negative potential is applied to the nontransparent film81, for example, holes are generated in the inner wall surfaces of the groove portion24in the substrate12, and accordingly, the effect to reduce dark current can be increased.

(First) Example where High-Refractive Material Portions are Provided

Next, a solid-state imaging device according to an eighth embodiment of the present disclosure is described.FIG. 13is a cross-sectional view of the main components of the solid-state imaging device90of this embodiment. The solid-state imaging device90of this embodiment differs from the solid-state imaging device1of the first embodiment in that high-refractive material portions91are formed on the color filter layers23. Therefore, inFIG. 13, the same components as those shown inFIG. 2are denoted by the same reference numerals as those used inFIG. 2, and explanation of them is not repeated herein. Also, the entire structure of the solid-state imaging device90of this embodiment is the same as the structure shown inFIG. 1, and therefore, explanation thereof will not be repeated herein.

In the solid-state imaging device90of this embodiment, the high-refractive material portions91made of a material having a higher refractive index than the device isolating portion27are formed on the color filter layers23. The high-refractive material portions91can be formed with a lens material, for example. The thickness of the high-refractive material portions91may be several hundreds of nanometers, and may be approximately equal to the width of the device isolating portion27in the direction parallel to the planar direction of the substrate12, for example.

The device isolating portion27is formed to extend from the light incidence surfaces of the high-refractive material portions91to the depth of the well regions13in the substrate12. That is, in this embodiment, the high-refractive material portions91are isolated from one another by the device isolating portion27between adjacent pixels2.

In a case where the high-refractive material portions91shown inFIG. 13are formed, the color filter layers23are first formed in the same manner as in the procedures of the first embodiment shown inFIGS. 3A through 4F, and the color filter layers23are partially removed so that the surfaces of the color filter layers23become closer to the substrate12than the surface of the device isolating portion27is. After that, a lens material is applied onto the color filter layers, to complete the solid-state imaging device90shown inFIG. 13.

In the solid-state imaging device90of this embodiment, the pixels2are isolated from one another by the device isolating portion27in the region extending from the high-refractive material portions91to the substrate12. Accordingly, in the solid-state imaging device90of this embodiment, a light collecting tube structure is formed, with the core being the high-refractive material portions91, the color filter layers23, and the photoelectric conversion units16formed in the substrate12, the cladding being the device isolating portion27.

In the solid-state imaging device90of this embodiment, the distance from the light incidence surface to the substrate is longer, because the high-refractive material portions91are provided. Therefore, light that enters the device isolating portion27is sufficiently absorbed by the color filter layers23forming the core, and then enters the photoelectric conversion units16. Accordingly, spectral characteristics are improved in the solid-state imaging device90of this embodiment. With the solid-state imaging device90of this embodiment, the same effects as those of the first embodiment can also be achieved.

(Second) Example where High-Refractive Material Portions are Provided

Next, a solid-state imaging device according to a ninth embodiment of the present disclosure is described.FIG. 14is a cross-sectional view of the main components of the solid-state imaging device100of this embodiment. The solid-state imaging device100of this embodiment differs from the solid-state imaging device1of the first embodiment in that high-refractive material portions101each having a rectangular shape in cross-section are formed on the color filter layers23. Therefore, inFIG. 14, the same components as those shown inFIG. 2are denoted by the same reference numerals as those used inFIG. 2, and explanation of them is not repeated herein. Also, the entire structure of the solid-state imaging device100of this embodiment is the same as the structure shown inFIG. 1, and therefore, explanation thereof will not be repeated herein.

In the solid-state imaging device100of this embodiment, the high-refractive material portions101formed on the color filter layers23each have a rectangular shape in cross-section, and are provided for the respective pixels2. Adjacent high-refractive material portions101are isolated from each other by a groove portion101a. The material of the high-refractive material portions101may be the same material as the lens material used in conventional solid-state imaging devices.

In the solid-state imaging device100of this embodiment, a light collecting tube structure is formed, with the core being the high-refractive material portions101, the color filter layers23, and the photoelectric conversion units16, the cladding being the groove portion101abetween the adjacent high-refractive material portions101and the device isolating portion27. Accordingly, with the solid-state imaging device1of this embodiment, the same effects as those of the eighth embodiment can also be achieved.

Example where On-Chip Lenses are Provided

Next, a solid-state imaging device according to a tenth embodiment of the present disclosure is described.FIG. 15is a cross-sectional view of the main components of the solid-state imaging device110of this embodiment. The solid-state imaging device110of this embodiment differs from the solid-state imaging device1of the first embodiment in that on-chip lenses111are provided on the color filter layers23. Therefore, inFIG. 15, the same components as those shown inFIG. 2are denoted by the same reference numerals as those used inFIG. 2, and explanation of them is not repeated herein. Also, the entire structure of the solid-state imaging device110of this embodiment is the same as the structure shown inFIG. 1, and therefore, explanation thereof will not be repeated herein.

In the solid-state imaging device110of this embodiment, the on-chip lenses111provided on the color filter layers23are designed to have spherical surfaces so that incident light is gathered into each corresponding pixel2. The on-chip lenses111can be formed by the same method as the method of manufacturing on-chip lenses of conventional solid-state imaging devices, after the color filter layers23are formed in the same manner as in the procedures of the first embodiment shown inFIGS. 3A through 4F.

In the solid-state imaging device110of this embodiment, incident light can be gathered into each corresponding pixel2, because the on-chip lenses111are provided. Accordingly, light collection efficiency can be improved, and sensitivity can be increased. In addition to the above effects, the same effects as those of the first embodiment can be achieved.

In the above described first through tenth embodiments, the first conductivity type is the n-type, the second conductivity type is the p-type, and electrons are used as signal charges. However, the present disclosure can also be applied in cases where holes are used as signal charges. In such cases, the conductivity types in each of the embodiments should be reversed. Solid-state imaging devices of the present disclosure are not limited to the above described first through tenth embodiments, and various combinations are possible without departing from the scope of the present disclosure.

The present disclosure is not necessarily applied to a solid-state imaging device that senses a distribution of visible incident light and captures the distribution as an image, but may also be applied to a solid-state imaging device that captures a distribution of infrared rays or X-rays or the like as an image.

Furthermore, the present disclosure is not limited to solid-state imaging devices that sequentially scan respective unit pixels in the pixel region by the row, and read pixel signals from the respective unit pixels. The present disclosure can also be applied to a solid-state imaging device of an X-Y address type that selects desired pixels one by one, and reads signals from the selected pixels one by one. A solid-state imaging device may be in the form of a single chip, or may be in the form of a module that is formed by packaging a pixel unit and a signal processing unit or an optical system, and has an imaging function.

A solid-state imaging device of the present disclosure can be used in an imaging apparatus. Here, an imaging apparatus is a camera system such as a digital still camera or a digital video camera, or an electronic apparatus that has an imaging function such as a portable telephone device. The form of the above described module mounted on an electronic apparatus, or a camera module, is an imaging apparatus in some cases.

Electronic Apparatus

Next, an electronic apparatus according to an eleventh embodiment of the present disclosure is described.FIG. 16is a schematic view of the structure of the electronic apparatus200according to the eleventh embodiment of the present disclosure.

The electronic apparatus200according to this embodiment includes a solid-state imaging device201, an optical lens203, a shutter device204, a drive circuit205, and a signal processing circuit206. The electronic apparatus200of this embodiment represents an embodiment in which the solid-state imaging device1of the above described first embodiment of the present disclosure is used as the solid-state imaging device201in an electronic apparatus (a digital still camera).

The optical lens203gathers image light (incident light) from an object and forms an image on the imaging surface of the solid-state imaging device201. With this, the signal charges are stored in the solid-state imaging device201for a certain period of time. The shutter device204controls the light exposure period and the light shielding period for the solid-state imaging device201. The drive circuit205supplies drive signals for controlling signal transfer operation of the solid-state imaging device201and shutter operation of the shutter device204. In accordance with a drive signal (a timing signal) supplied from the drive circuit205, the solid-state imaging device201performs signal transfer. The signal processing circuit206performs various kinds of signal processing on signals output from the solid-state imaging device201. Video signals subjected to the signal processing are stored into a storage medium such as a memory, or are output to a monitor.

In the electronic apparatus200of this embodiment, light collection characteristics and sensitivity are improved in the solid-state imaging device201, and image quality can be improved accordingly. Although the solid-state imaging device1of the first embodiment is used as the solid-state imaging device201in this embodiment, it is also possible to use any of the solid-state imaging devices according to the second through tenth embodiments.

The present disclosure can also be embodied in the structures described below.

A solid-state imaging device including:

a substrate;

pixels each including a photoelectric conversion unit formed in the substrate;

a color filter layer provided on the light incidence surface side of the substrate; and

a device isolating portion that is formed to divide the color filter layer and the substrate for the respective pixels, and has a lower refractive index than the color filter layer and the substrate.

The solid-state imaging device of (1), wherein the device isolating portion includes a groove portion formed to extend from the color filter layer to the substrate, and an insulating film that is buried in the groove portion and is made of a material having a lower refractive index than the color filter layer and the substrate.

The solid-state imaging device of (2), wherein the device isolating portion further includes a film between the inner wall surface of the groove portion and the insulating film, the film being formed to cover the inner wall surface of the groove portion, the film containing fixed charges of the opposite polarity to the polarity of signal charges stored in the photoelectric conversion units, the film being made of a material having a lower refractive index than the color filter layer and the substrate.

The solid-state imaging device of any one of (1) through (3), wherein the device isolating portion protrudes from the light incidence surface of the color filter layer.

The solid-state imaging device of any one of (1) through (4), further including a high-refractive material portion formed on the color filter layer, the high-refractive material portion being made of a material having a higher refractive index than the refractive index of the color filter layer, the high-refractive material portion being divided for the respective pixels.

The solid-state imaging device of any one of (1) through (5), wherein the device isolating portion is placed in the region of the pixel isolating portion formed to divide the substrate for the respective pixels.

The solid-state imaging device of any one of (1) through (6), further including a light scattering structure on the light incidence surface side of the photoelectric conversion units.

The solid-state imaging device of any one of (1) through (7), wherein the color filter layer has a thickness of 1 μm or greater.

The solid-state imaging device of any one of (2) through (8), wherein a metal material is buried in the groove portion via the insulating film.

The solid-state imaging device of (9), wherein the metal material serves as a nontransparent film.

The solid-state imaging device of any one of (1) through (10), wherein a light absorbing portion is formed on the light incidence surface side of the device isolating portion.

The solid-state imaging device of any one of (1) through (11), wherein an on-chip lens is formed on the color filter layer.

The solid-state imaging device of (1), wherein the device isolating portion is formed with a groove portion extending from the color filter layer to the substrate.

The solid-state imaging device of any one of (1) through (13), further including a film formed to cover the inner wall surface of the groove portion, the film containing negative fixed charges, the film being made of a material having a lower refractive index than the color filter layer and the substrate.

A method of manufacturing a solid-state imaging device, including:

the step of forming photoelectric conversion units in a substrate, the photoelectric conversion units corresponding to respective pixels;

the step of forming a color filter layer on the light incidence surface side of the substrate; and

the step of forming a device isolating portion in the region to divide the color filter layer and the substrate for the respective pixels, the device isolating portion having a lower refractive index than the color filter layer and the substrate, the device isolating portion being formed prior to or after the formation of the color filter layer.

The method of (15), wherein the device isolating portion dividing the color filter layer for the respective pixels and the device isolating portion dividing the substrate for the respective pixels are formed in the same step.

The method of (15) or (16), wherein

the step of forming the device isolating portion includes:

the step of forming a groove portion, prior to the formation of the color filter layer, by forming a mask on the light incidence surface side of the substrate and performing etching on the substrate via the mask, the mask having an opening in the portion corresponding to the region in which the device isolating portion is to be formed;

the step of forming an insulating film in the groove portion formed in the substrate and the opening of the mask; and

the step of removing the mask, and

the color filter layer is formed in a concave portion after the mask is removed, the concave portion being formed by the substrate and the insulating film designed to protrude from the substrate.

The method of (15) or (16), wherein the step of forming the device isolating portion includes the step of forming a groove portion, after the formation of the color filter layer, by forming a mask on the color filter layer and performing etching on the color filter layer and the substrate via the mask, the mask having an opening in the portion corresponding to the region in which the device isolating portion is to be formed.

The method of (15) or (16), wherein the step of forming the device isolating portion includes the step of performing etching on the substrate after the formation of the color filter layer, the mask being the color filter layer divided for the respective pixels and being isolated between adjacent pixels.

An electronic apparatus including:

a solid-state imaging device; and

a signal processing circuit that processes an output signal that is output from the solid-state imaging device,

the solid-state imaging device including: a substrate; pixels each including a photoelectric conversion unit formed in the substrate; a color filter layer provided on the light incidence surface side of the substrate; and a device isolating portion that is formed to divide the color filter layer and the substrate for the respective pixels, and has a lower refractive index than the color filter layer and the substrate.

REFERENCE SIGNS LIST