JP4923456B2 - Solid-state imaging device, manufacturing method thereof, and camera - Google Patents

Description

  The present invention particularly relates to a solid-state imaging device including an on-chip lens, a manufacturing method thereof, and a camera including the solid-state imaging device.

  In a CCD type or MOS type solid-state imaging device, each pixel tends to be miniaturized. As a result, the area of the light receiving portion in the pixel is reduced, and the photoelectric conversion characteristic, that is, the photosensitivity, which is one of the characteristics of the solid-state imaging device, is reduced.

  In order to improve the photosensitivity of the solid-state imaging device, a technique has been introduced in which a microlens is provided at a position corresponding to each light receiving unit and incident light is efficiently condensed on the light receiving unit (see Patent Documents 1 and 2). .

In the solid-state imaging device described in Patent Document 1, a transparent resin is formed on a microlens made of an organic resin. In the solid-state imaging device described in Patent Document 2, a transparent resin is formed on a microlens made of silicon nitride. As the transparent resin, a resin having a refractive index lower than that of the microlens is used.
Japanese Patent Laid-Open No. 10-270672 JP 2003-338613 A

  In order to refract the incident light by the microlens and improve the light collecting characteristic, it is necessary to have a refractive index difference between the microlens and the transparent resin thereon.

  However, in Patent Document 1, since both the microlens and the transparent resin thereon are formed of an organic resin, the refractive index difference between the microlens and the transparent resin can be ensured only to about 0.4.

  In Patent Document 2, since the microlens is inorganic silicon nitride (refractive index of about 2.0) and the transparent resin is epoxy resin (refractive index of 1.5), the refractive index difference is about 0.5. . However, in Patent Document 2, it is necessary to process silicon nitride into a lens shape by whole surface dry etching using a resist mask. In this whole surface dry etching, it is difficult to set the etching selectivity of silicon nitride to the resist mask to 1. It becomes. When the etching selection ratio is increased, the ineffective area (gap between lenses) of the microlens is increased, and the light condensing characteristic is deteriorated. In addition, there is a problem that the dark current of the solid-state imaging device increases due to plasma damage during dry etching.

The present invention has been made in view of the above circumstances, and the purpose thereof is to secure a refractive index difference between the microlens and the transparent protective film and eliminate a gap between the microlenses, thereby collecting light. An object of the present invention is to provide a solid-state imaging device and a camera with improved performance.
Another object of the present invention is to provide a method for manufacturing a solid-state imaging device having a microlens that ensures a difference in refractive index between the microlens and the transparent protective film and eliminates a gap without using a dry etching technique. It is in.

  In order to achieve the above object, a solid-state imaging device according to the present invention includes a plurality of light receiving portions formed on a substrate, a microlens formed on the substrate and corresponding to each light receiving portion, And a transparent protective film having a refractive index lower than that of the microlens. The microlens is adjacent to a first lens layer formed of a lens-shaped resin containing refractive index adjusting particles. And an inorganic second lens layer formed so as to cover the first lens layer so as to fill a gap between the first lens layers.

In the solid-state imaging device according to the present invention, the microlens includes the first lens so as to embed a gap between the first lens layer formed of the lens-shaped resin containing the refractive index adjusting particles and the adjacent first lens layers. And an inorganic second lens layer formed by covering the layer. The organic resin generally has a lower refractive index than that of an inorganic material, but in the present invention, the refractive index of the first lens layer can be changed by dispersing the refractive index adjusting particles in the resin, thereby changing the refractive index of the original resin. Can be larger. For this reason, the refractive index of the microlens formed by the first lens layer and the inorganic second lens layer can be increased. For this reason, the difference in refractive index between the microlens and the transparent protective film thereon can be secured.
Further, by filling the gap between the adjacent first lens layers with the second lens layer, the ineffective area of the microlens formed by the first lens layer and the second lens layer, that is, the gap is eliminated.

  In order to achieve the above object, a method of manufacturing a solid-state imaging device according to the present invention includes a step of forming a plurality of light receiving portions on a substrate, and a photosensitive resin containing refractive index adjusting particles on an upper layer of the substrate. A step of forming one lens layer, a step of exposing and developing the first lens layer to process it into a first lens layer having a pattern corresponding to each of the light receiving portions, and a lens for forming the first lens layer by heat treatment. Forming the shape, forming an inorganic second lens layer that covers the first lens layer so as to fill a gap between the adjacent first lens layers, and on the second lens layer, Forming a transparent protective film having a refractive index smaller than that of the first lens layer and the second lens layer.

  In the manufacturing method of the solid-state imaging device of the present invention, the first lens layer is made of the photosensitive resin containing the refractive index adjusting particles, so that the first corresponding to the light receiving portion is formed by exposure, development, and heat treatment. Can be processed into a lens layer. Then, a microlens having a laminated structure of the first lens layer and the second lens layer is formed by forming an inorganic second lens layer that covers the first lens layer so as to fill a gap between the adjacent first lens layers. Is formed. Thus, in the present invention, the lens shape can be obtained without using the dry etching technique.

  In order to achieve the above object, a camera of the present invention includes a solid-state imaging device, an optical system that focuses light on the imaging surface of the solid-state imaging device, and a predetermined signal with respect to an output signal from the solid-state imaging device. A signal processing circuit that performs processing, and the solid-state imaging device includes a plurality of light receiving portions formed on a substrate, a microlens formed on the substrate and corresponding to each light receiving portion, The microlens is covered with a transparent protective film having a refractive index lower than that of the microlens, and the microlens is formed of a lens-shaped resin containing refractive index adjusting particles; And an inorganic second lens layer formed so as to cover the first lens layer so as to fill a gap between the adjacent first lens layers.

In the camera of the present invention described above, the microlens of the solid-state imaging device is configured to embed a gap between the first lens layer formed of a lens-shaped resin containing refractive index adjusting particles and the adjacent first lens layers. And an inorganic second lens layer formed by covering the first lens layer. The organic resin generally has a lower refractive index than that of an inorganic material, but in the present invention, the refractive index of the first lens layer can be changed by dispersing the refractive index adjusting particles in the resin, thereby changing the refractive index of the original resin. Can be larger. For this reason, the refractive index of the microlens formed by the first lens layer and the inorganic second lens layer can be increased. For this reason, the difference in refractive index between the microlens and the transparent protective film thereon can be secured.
Further, by filling the gap between the adjacent first lens layers with the second lens layer, the ineffective area of the microlens formed by the first lens layer and the second lens layer, that is, the gap is eliminated.

ADVANTAGE OF THE INVENTION According to this invention, the solid-state imaging device and camera which improved the condensing characteristic by ensuring the refractive index difference between a microlens and a transparent protective film, and eliminating the clearance gap between microlenses are realizable.
According to the method for manufacturing a solid-state imaging device of the present invention, a solid-state imaging device having a microlens that secures a refractive index difference between the microlens and the transparent protective film and eliminates a gap without using dry etching technology. can do.

  Embodiments of the present invention will be described below with reference to the drawings. In each figure, the same components are denoted by the same reference numerals. In the present embodiment, an example in which the present invention is applied to an interline transfer type CCD (Charge Coupled Device) type solid-state imaging device will be described. However, there is no particular limitation on the transfer method.

(First embodiment)
FIG. 1 is a schematic configuration diagram of a solid-state imaging apparatus according to the present embodiment. The solid-state imaging device 1 according to the present embodiment includes an imaging unit 2, a horizontal transfer unit 3, and an output unit 4.

  The imaging unit 2 includes a plurality of light receiving units 5 arranged in a matrix for each pixel, a plurality of vertical transfer units 7 arranged for each vertical column of the light receiving unit 5, and the light receiving units 5 and the vertical transfer units 7. And a read gate portion 6 disposed between the two.

  The light receiving unit 5 includes, for example, a photodiode, and photoelectrically converts image light (incident light) incident from a subject into signal charges having a charge amount corresponding to the light amount and accumulates the signal light. The read gate unit 6 reads the signal charges accumulated in the light receiving unit 5 to the vertical transfer unit 7.

  The vertical transfer unit 7 is driven by four-phase clock signals φV1, φV2, φV3, and φV4, and transfers the signal charges read from the light receiving unit 5 in the vertical direction (downward in the figure). The clock signal is not limited to four phases. The clock signals φV1 to φV4 are, for example, 0V or −8.5V.

  The horizontal transfer unit 3 is driven by the two-phase clock signals φH1 and φH2, and transfers the signal charges vertically transferred from the vertical transfer unit 7 in the horizontal direction (left direction in the figure).

  The vertical transfer unit 7 and the horizontal transfer unit 3 include a transfer channel formed in the transfer direction formed on the substrate, and a plurality of transfer electrodes formed side by side in the transfer direction with an insulating film interposed on the transfer channel. Have.

  The output unit 4 includes, for example, a charge-voltage conversion unit 4a configured by floating diffusion, converts the signal charge horizontally transferred by the horizontal transfer unit 3 into an electric signal, and outputs the signal as an analog image signal.

  FIG. 2 is a plan view of the main part of the imaging unit 2.

  A transfer channel 14 extending in the transfer direction is formed adjacent to the light receiving portions 5 arranged in a matrix. On the transfer channel 14, the first transfer electrode 21 and the second transfer electrode 22 are alternately and repeatedly arranged in the transfer direction with an insulating film interposed therebetween. When there is no need to distinguish between the first transfer electrode 21 and the second transfer electrode 22, they are simply referred to as the transfer electrode 20. The vertical transfer unit 7 is configured by the transfer channel 14 and the transfer electrode 20. The first transfer electrode 21 and the second transfer electrode 22 arranged in the transfer direction are arranged so that the ends thereof overlap each other.

  The first transfer electrode 21 and the second transfer electrode 22 in the horizontal direction are connected to each other. The first transfer electrode 21 is formed of a first polysilicon layer, and the second transfer electrode 22 is formed of a second polysilicon layer. In this embodiment, an example of a transfer electrode having a two-layer structure will be described. However, a single-layer structure or a structure having three or more layers may be used.

  When a voltage is applied to the first transfer electrode 21 and the second transfer electrode 22, a potential well is formed in the transfer channel 14. The clock signals φV1, V2, V3, and V4 for forming the potential well are applied to the first transfer electrode 21 and the second transfer electrode 22 arranged in the transfer direction with a phase shift, so that the potential The distribution of the wells changes sequentially, and the charges in the potential well are transferred along the transfer direction.

  FIG. 3 is a cross-sectional view of a main part of the solid-state imaging device according to the present embodiment. FIG. 3 corresponds to a cross-sectional view taken along line A-A ′ of FIG. 2.

  For example, a p-type well 11 is formed on an n-type silicon substrate (hereinafter referred to as substrate 10). The p-type well 11 forms an overflow barrier.

The light receiving unit 5 includes an n-type signal charge storage region 12 formed in the p-type well 11 and a p ⁺ -type hole storage region 13 formed in the surface layer of the signal charge storage region 12. The hole accumulation region 13 is provided in order to suppress dark current that is generated near the surface of the signal charge accumulation region 12 and becomes a noise source.

  In the light receiving portion 5, an npn structure is formed by the signal charge accumulation region 12, the p-type well 11 and the substrate 10. This npn structure is a vertical overflow drain that discharges signal charges to the substrate 10 side when signal light generated excessively due to strong light incident on the light receiving section 5 exceeds an overflow barrier formed by the p-type well 11. Configure the structure.

  Further, the light receiving unit 5 has a function of an electronic shutter. That is, by setting the substrate potential supplied to the substrate 10 to a high level (for example, +12 V), the potential barrier of the p-type well 11 is lowered, and the charge accumulated in the signal charge accumulation region 12 overcomes the potential barrier, It is swept away in the vertical direction, that is, the substrate 10. Thereby, the exposure period can be adjusted.

  The vertical transfer unit 7 includes an n-type transfer channel 14 formed in the p-type well 11 at a predetermined interval from the signal charge storage region 12, and a gate insulating film 18 made of a silicon oxide film on the transfer channel 14. The transfer electrode 20 is made of, for example, polysilicon. A relatively high concentration p-type region 15 is formed under the transfer channel 14. The p-type region 15 forms a potential barrier under the transfer channel 14. For this reason, the signal charge photoelectrically converted in the deep portion of the substrate 10 is prevented from entering the transfer channel 14, and the occurrence of smear is suppressed.

  The read gate unit 6 includes a p-type read gate region 16 between the signal charge storage region 12 and the transfer channel 14 and a transfer electrode 20 formed on the read gate region 16 via a gate insulating film 18. ing. The read gate region 16 forms a potential barrier between the n-type signal charge storage region 12 and the transfer channel 14. At the time of reading, a positive read voltage (for example, 15 V) is applied to the transfer electrode, the potential barrier of the read gate region 16 is lowered, and the signal charge is transferred from the signal charge storage region 12 to the transfer channel 14.

  A p-type channel stop region 17 is formed on the side opposite to the reading side with respect to the signal charge storage region 12. The channel stop region 17 forms a potential barrier against the signal charge and prevents the signal charge from flowing in and out.

  A light shielding film 24 that covers the transfer electrode 20 is formed on the transfer electrode 20 via an insulating film 23 made of, for example, silicon oxide. The light shielding film 24 is made of a refractory metal such as tungsten, for example. The light shielding film 24 has an opening for allowing light to enter the light receiving portion 5.

  On the light shielding film 24, a first interlayer insulating film 25 made of, for example, BPSG (Boro Phospho Silicate glass) is formed. In the first interlayer insulating film 25, irregularities due to the surface step of the base are formed. A second interlayer insulating film 26 made of a material having a higher refractive index than that of the first interlayer insulating film 25 is formed on the first interlayer insulating film 25. The second interlayer insulating film 26 is made of, for example, silicon nitride. The surface of the second interlayer insulating film 26 is planarized. An inner lens is formed by the interface between the first interlayer insulating film 25 and the second interlayer insulating film 26.

  A color filter 30 is formed on the second interlayer insulating film 26. The color filter 30 is, for example, a primary color type, and includes a green color filter 31, a blue color filter 32, and a red color filter 33. In the case of the complementary color type, the color filter 30 is formed of cyan, magenta, yellow, and green color filters.

  On the color filter 30, a planarizing film 40 made of, for example, an acrylic thermosetting resin is formed. A micro lens 50 is formed on the planarizing film 40.

  The microlens 50 includes a first lens layer 51 and a second lens layer 52. The refractive indexes of the first lens layer 51 and the second lens layer 52 are adjusted to be substantially the same. The refractive index of the microlens 50 is 1.85 to 2.10. The thickness D of the microlens 50 is, for example, 550 nm.

  The 1st lens layer 51 is arrange | positioned corresponding to each light-receiving part 5, and is processed into the lens shape. The first lens layer 51 is made of a photosensitive resin containing metal oxide particles. The metal oxide particles are an embodiment of the refractive index adjusting particles of the present invention. The photosensitive resin is, for example, a polyimide resin.

  The refractive index of the first lens layer 51 is adjusted by changing the addition amount of the metal oxide particles. That is, if the addition amount of the metal oxide particles is increased, the refractive index of the first lens layer 51 is increased. The metal oxide particles are, for example, zinc oxide, zirconium oxide, niobium oxide, titanium oxide, and tin oxide.

  The second lens layer 52 is formed on the entire surface so as to cover the gap between the first lens layers 51 and the first lens layer 51. The second lens layer 52 eliminates a gap (invalid area) between the microlenses 50. The second lens layer 52 is made of, for example, silicon nitride.

  A transparent protective film 60 having a refractive index lower than that of the microlens 50 is formed so as to cover the microlens 50. The surface of the transparent protective film 60 is flattened. The transparent protective film 60 is made of, for example, an organic polymer material containing fluorine, organic SOG (Spin on Glass), acrylic resin, epoxy resin, or the like. The refractive index of the transparent protective film 60 is 1.34 to 1.50.

  The microlens 50 (refractive index of 1.85 to 2.10) and the transparent protective film 60 (refractive index of 1.34 to 1.50) can ensure a refractive index difference of 0.4 or more. In addition, a maximum refractive index difference of about 0.76 can be ensured by a combination of materials.

  In the solid-state imaging device described above, incident light is collected by the microlens 50 and reaches the color filters 31, 32, and 33. Only light in a predetermined wavelength region passes through each color filter, is further condensed by an inner lens formed by the interface between the first interlayer insulating film 25 and the second interlayer insulating film 26, and enters the light receiving unit 5. . The light incident on the light receiving unit 5 is photoelectrically converted into a signal charge corresponding to the amount of incident light and accumulated in the signal charge accumulation region 12. Thereafter, the data is read out to the transfer channel 14 and transferred in the vertical direction by the vertical transfer unit 7.

  Next, a method for manufacturing the solid-state imaging device according to the present embodiment will be described with reference to FIGS.

  As shown in FIG. 4A, a p-type well 11, an n-type signal charge storage region 12, an n-type transfer channel 14, and a p-type region 15 are formed on a substrate 10 made of n-type silicon by ion implantation. , A p-type read gate region 16 and a p-type channel stop region 17 are formed. Subsequently, a gate insulating film 18 made of silicon oxide is formed on the substrate 10 by a thermal oxidation method.

  Next, as shown in FIG. 4B, the transfer electrode 20 is formed on the gate insulating film 18. The transfer electrode 20 is formed by depositing polysilicon and then etching the polysilicon using a resist. When the transfer electrode 20 has a two-layer structure, an insulating film is formed between the first and second transfer electrodes. After the transfer electrode 20 is formed, an insulating film 23 made of silicon oxide that covers the transfer electrode 20 is formed by, for example, a CVD method. Subsequently, the p-type hole accumulation region 13 is formed in the surface layer of the signal charge accumulation region 12 by ion implantation using the transfer electrode 20 as a mask. As a result, the light receiving portion 5, the read gate portion 6 and the vertical transfer portion 7 are formed on the substrate 10.

  Next, as shown in FIG. 5A, a light shielding film 24 having an opening 24a at the position of the light receiving portion 5 and covering the transfer electrode 20 is formed. The light shielding film 24 is formed, for example, by depositing a refractory metal film such as tungsten on the substrate 10 and processing the refractory metal film by dry etching using a resist mask.

  Next, as shown in FIG. 5B, a first interlayer insulating film 25 is formed by depositing, for example, BPSG on the substrate 10 and performing a reflow process. Subsequently, a silicon nitride film is deposited on the first interlayer insulating film 25 by a plasma CVD method, and the second interlayer insulating film 26 is formed by planarizing the surface of the silicon nitride film.

  Next, as shown in FIG. 6A, the color filter 30 is formed on the second interlayer insulating film 26. The color filter 30 is formed using, for example, a color resist method. For example, after the green color resist is formed on the second interlayer insulating film 26, the green color resist is exposed and developed to form a pattern of the green color filter 31. Similarly, the blue color filter 32 and the red color filter 33 are formed by performing color resist formation, exposure, and development. Note that the order of forming the color filters 30 is not limited.

  Next, as shown in FIG. 6B, a transparent flattening film 40 is formed on the color filter 30 for the purpose of flattening the surface unevenness of the color filter 30. As the planarization film 40, for example, an acrylic thermosetting resin is used.

  Next, as shown in FIG. 7A, a photosensitive resin in which metal oxide particles are dispersed is applied onto the planarizing film 40 by a spin coating method to form the first lens layer 51a. As the photosensitive resin, a polyimide resin containing a photosensitive agent is used.

  Next, as shown in FIG. 7B, the first lens layer 51b corresponding to the light receiving unit 5 is processed by exposure and development. Here, it is not necessary that all the first lens layers 51a are formed immediately above the light receiving unit 5, and pupil correction may be performed. The pupil correction is a technique for slightly moving the position of the first lens layer 51b toward the center in the peripheral part of the imaging unit 2.

  Next, as shown in FIG. 8A, a lens-shaped first lens layer 51 is formed by heat treatment. In this example, the first lens layer 51 made of a photosensitive resin containing a metal oxide is formed into a microlens shape by using a phenomenon (20-30%) that shrinks when the polyimide precursor is converted into a polyimide by heat treatment. . The heat treatment is performed at a temperature of 200 ° C. for 5 minutes using a hot plate. When forming the micro lens 50 having a thickness D of 550 nm (see FIG. 3), the thickness E of the first lens layer 51 after the heat treatment is set to 300 nm. Since the first lens layer 51 is processed into a lens shape using a contraction phenomenon, an ineffective region having a width W is generated. The width W varies depending on the exposure condition when processing the first lens layer 51b, but the condition is set such that the width W is 500 nm, for example.

  Next, as shown in FIG. 8B, the second lens layer 52 is formed on the first lens layer 51 so as to fill the gap between the adjacent first lens layers 51. As the second lens layer 52, a silicon nitride film is formed by plasma CVD, for example. Examples of the plasma CVD method include HDP-CVD (High Density Plasma Chemical Vapor Deposition), CAT-CVD (Catalytic Chemical Vapor Deposition), and ICP-CVD (Inductively Coupled Plasma Chemical Vapor Deposition).

  For example, a silicon nitride film having a thickness of 300 nm and a refractive index of about 1.95 is formed by HDP-CVD at a film formation temperature of 140 ° C. and a film formation time of 3 minutes. The thickness of the silicon nitride film is preferably greater than W / 2 with respect to the width W of the ineffective region of the first lens layer 51. Further, it is necessary to consider the difference in film forming speed between the vertical direction (H direction in the figure) and the horizontal direction (I direction in the figure) in the CVD method. As a result of examining the vertical and horizontal film forming speeds, the vertical film forming speed was 1 and the horizontal film forming speed was 0.9. Therefore, when the width W of the ineffective area is 500 nm, if the film is formed at 277 nm, the microlens 50 having substantially zero ineffective area is formed. In this embodiment, a margin is set and the film forming conditions are set to 300 nm.

  Next, a transparent protective film 60 having a refractive index lower than that of the microlens 50 is formed on the microlens 50 by spin coating (see FIG. 3). Examples of the material of the transparent protective film 60 include organic polymer materials containing fluorine, organic SOG, acrylic resin, and epoxy resin. In the present embodiment, a fluorine resin is used. After the heat treatment, the thickness of the transparent protective film 60 is set so that a substantially flat transparent protective film 60 is obtained between the peripheral portion of the imaging unit 2 without the microlens 50 and the imaging unit 2 with the microlens 50. Set. For example, the film thickness of 2300 nm or more is required to obtain the flat transparent protective film 60 after the heat treatment at 200 ° C. for 5 minutes. For this reason, for example, the film was formed under the condition of 2500 nm. The refractive index of the transparent protective film 60 was adjusted to 1.38.

  FIG. 9 is a cross-sectional view when the thickness of the second lens layer 52 is greater than the thickness of the second lens layer 52 shown in FIG.

  When the radius of curvature of the microlens 50 is set to r (see FIG. 8B) when the film thickness of the second lens layer 52 is set so that the width W of the invalid region is filled, the second lens layer 52 is formed thicker. As a result, the radius of curvature of the microlens 50 becomes r ′ larger than r. Thus, by changing the film thickness of the second lens layer 52, the focal length of the microlens 50 can be adjusted, and the microlens can be optimized for various solid-state imaging devices.

  As described above, the solid-state imaging device according to this embodiment is manufactured. The solid-state imaging device is used for a camera such as a video camera, a digital still camera, or an electronic endoscope camera, for example.

  FIG. 10 is a schematic configuration diagram of a camera in which the above-described solid-state imaging device is used.

  The camera 100 includes the solid-state imaging device 1 described above, an optical system 102, a drive circuit 103, and a signal processing circuit 104.

  The optical system 102 forms image light (incident light) from the subject on the imaging surface of the solid-state imaging device 1. Thereby, in each light receiving unit 5 of the solid-state imaging device 1, incident light is converted into a signal charge corresponding to the amount of incident light, and the signal charge is accumulated in the signal charge accumulation region 12 of the light receiving unit 5 for a certain period.

  The drive circuit 103 supplies various timing signals such as the above-described four-phase clock signals φV1, φV2, φV3, φV4 and two-phase clock signals φH1, φH2 to the solid-state imaging device 1. As a result, various types of driving such as signal charge readout, vertical transfer, and horizontal transfer of the solid-state imaging device 1 are performed. Further, by this driving, an analog image signal is output from the output unit 4 of the solid-state imaging device 1.

  The signal processing circuit 104 performs various kinds of signal processing such as noise removal or conversion into a digital signal on the analog image signal output from the solid-state imaging device 1. After the signal processing by the signal processing circuit 104 is performed, it is stored in a storage medium such as a memory.

  Next, the solid-state imaging device according to the present embodiment, the manufacturing method thereof, and the effects of the camera will be described.

  In the solid-state imaging device according to the present embodiment, the microlens 50 embeds a gap between the first lens layer 51 formed of a lens-shaped resin containing metal oxide particles and the adjacent first lens layers 51. In addition, an inorganic second lens layer 52 formed by covering the first lens layer 51 is formed. A transparent protective film 60 having a refractive index lower than that of the microlens 50 is formed so as to cover the microlens 50.

  The organic resin generally has a lower refractive index than that of an inorganic material. However, in this embodiment, the refractive index of the first lens layer 51 is reduced by dispersing metal oxide particles in the resin. It can be larger than the refractive index. Therefore, the refractive index of the microlens 50 formed by the first lens layer 51 and the inorganic second lens layer 52 can be increased. For this reason, the refractive index difference between the microlens 50 and the transparent protective film 60 thereon can be secured, the light condensing characteristics of the microlens 50 can be improved, and the light sensitivity can be improved.

  Further, by filling the gap between the first lens layers 51 with the second lens layer 52, the ineffective area of the microlens 50 formed by the first lens layer 51 and the second lens layer 52 can be eliminated. As a result, the condensing characteristic of the microlens 50 can be improved, and the photosensitivity can be improved.

  There is also a refractive index difference between the transparent protective film 60 and the surrounding air. That is, the transparent protective film 60 is larger than the refractive index of the surrounding air. For this reason, the light incident obliquely on the surface of the transparent protective film 60 is refracted, and the angle of the incident light can be reduced. As a result, light can be further refracted by the microlens 50 and incident light can be condensed on the light receiving unit 5, so that the photosensitivity can be improved.

  In the manufacturing method of the solid-state imaging device according to the present embodiment, the first lens layer 51 is made of a photosensitive resin containing metal oxide particles, so that the first lens layer 51 is arranged corresponding to the light receiving unit by exposure, development, and heat treatment. One lens layer 51 can be processed. Then, an inorganic second lens layer 52 that covers the first lens layer 51 is formed so as to fill a gap between the first lens layers 51. In this embodiment, since the lens shape can be obtained without using the dry etching technique, there is no deterioration in characteristics such as an increase in dark current due to plasma damage during dry etching.

  As described above, according to the solid-state imaging device according to the present embodiment, a difference in refractive index between the microlens 50 and the transparent protective film 60 can be ensured, and a gap between the microlenses can be eliminated. A solid-state imaging device with improved optical characteristics can be realized.

  In addition, in the camera 30 such as a video camera or a digital still camera, the camera 100 with improved photosensitivity can be realized by using the solid-state imaging device 1 with improved photosensitivity.

  In addition, according to the method for manufacturing the solid-state imaging device according to the present embodiment, it is possible to ensure the difference in refractive index between the microlens 50 and the transparent protective film 60 without using a dry etching technique, and eliminate the gap. A solid-state imaging device having the microlens 50 can be manufactured.

(Second Embodiment)
FIG. 11 is a cross-sectional view of the solid-state imaging device according to the second embodiment. FIG. 11 corresponds to a cross-sectional view taken along line AA ′ of FIG.

  In the solid-state imaging device according to the present embodiment, an antireflection film 70 is formed on the transparent protective film 60 in order to prevent reflection of incident light on the transparent protective film 60. The antireflection film 70 is formed of a material having a refractive index lower than that of the transparent protective film 60.

  According to the solid-state imaging device and the manufacturing method thereof according to the above-described embodiment, since the antireflection film 70 is formed on the transparent protective film 60, the amount of light that is incident on the light receiving unit 5 after reflecting incident light is reflected. Reduction can be suppressed. As a result, a solid-state imaging device with improved photosensitivity can be realized.

(Third embodiment)
FIG. 12 is a cross-sectional view of the solid-state imaging device according to the third embodiment. 12 corresponds to a cross-sectional view taken along line AA ′ in FIG.

  In the solid-state imaging device according to the present embodiment, an antireflection film 70 is formed on the microlens 50 in order to prevent reflection of incident light on the microlens 50. A transparent protective film 60 is formed on the antireflection film 70. The antireflection film 70 is formed of a material having a refractive index higher than that of the transparent protective film 60 and lower than that of the microlens 50.

  According to the solid-state imaging device and the manufacturing method thereof according to the above-described embodiment, since the antireflection film 70 is formed on the microlens 50, the amount of incident light reflected and incident on the light receiving unit 5 is reduced. Can be suppressed. As a result, a solid-state imaging device with improved photosensitivity can be realized.

(Fourth embodiment)
FIG. 13A is a plan view of the solid-state imaging device according to the fourth embodiment, and FIG. 13B is a cross-sectional view taken along the line BB ′ in FIG. In FIG. 13B, only the configuration of the upper layer than the color filter 30 is illustrated.

  As shown in FIG. 13A, microlenses 50 are arranged in a matrix so as to correspond to the light receiving portions. Oxygen supply holes 52 a are formed in the second lens layer 52 in the corners of the microlenses 50, that is, the regions between the microlenses adjacent in the diagonal direction. The oxygen supply holes 52a need not be formed in all four corners of the microlens 50.

  The oxygen supply hole 52a is formed by dry etching using a resist mask after the second lens layer 52 is formed. The oxygen supply hole 52a may penetrate the planarizing film 40. Here, as compared with the entire surface dry etching for obtaining the conventional lens shape, the plasma etching can be reduced because the dry etching at the time of patterning the oxygen supply hole 52a is locally performed. For this reason, generation | occurrence | production of a dark current can be suppressed.

  Silicon nitride used as the second lens layer 52 serves as an oxygen blocking film. Here, for the green color filter 31, for example, copper phthalocyanine is used as a pigment. This copper phthalocyanine is vulnerable to a reduction reaction. That is, copper phthalocyanine is decomposed by the reduction reaction. Note that there is no particular limitation as long as the color filter 30 has a pigment that is decomposed by a reduction reaction.

  In the present embodiment, since the oxygen supply hole 52a is formed in the second lens layer 52, oxygen can be supplied to the color filter 30 through the oxygen supply hole 52a. For this reason, when the color filter 30 having a pigment that decomposes due to the reduction reaction is employed, the characteristics of the color filter 30 can be maintained over a long period of time.

The present invention is not limited to the description of the above embodiment. The present invention can be applied to a solid-state imaging device of a frame transfer system or a frame interline transfer system in addition to the interline transfer system. Further, the present invention can be applied to a MOS type solid-state imaging device in addition to a CCD type solid-state imaging device. Moreover, although the example using the metal oxide particles as the refractive index adjusting particles has been described, other particles capable of adjusting the refractive index may be used.
In addition, various modifications can be made without departing from the scope of the present invention.

It is a schematic block diagram which shows an example of the solid-state imaging device concerning this embodiment. It is a principal part top view of an imaging part. It is sectional drawing of the solid-state imaging device which concerns on 1st Embodiment. It is process sectional drawing in manufacture of the solid-state imaging device which concerns on 1st Embodiment. It is process sectional drawing in manufacture of the solid-state imaging device which concerns on 1st Embodiment. It is process sectional drawing in manufacture of the solid-state imaging device which concerns on 1st Embodiment. It is process sectional drawing in manufacture of the solid-state imaging device which concerns on 1st Embodiment. It is process sectional drawing in manufacture of the solid-state imaging device which concerns on 1st Embodiment. It is sectional drawing which shows the modification of the solid-state imaging device which concerns on 1st Embodiment. It is a block diagram which shows schematic structure of the camera with which the solid-state imaging device which concerns on this embodiment is applied. It is sectional drawing of the solid-state imaging device which concerns on 2nd Embodiment. It is sectional drawing of the solid-state imaging device which concerns on 3rd Embodiment. (A) is a top view of the solid-state imaging device concerning a 4th embodiment, and (b) is a sectional view in the B-B 'line of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Solid-state imaging device, 2 ... Imaging part, 3 ... Horizontal transfer part, 4 ... Output part, 4a ... Charge-voltage conversion part, 5 ... Light-receiving part, 6 ... Read-out gate part, 7 ... Vertical transfer part, 10 ... Board | substrate 11 ... p-type well, 12 ... signal charge storage region, 13 ... hole storage region, 14 ... transfer channel, 15 ... p-type region, 16 ... read gate region, 17 ... channel stop region, 18 ... gate insulating film 18 ... Transfer electrode, 21 ... First transfer electrode, 22 ... Second transfer electrode, 23 ... Insulating film, 24 ... Light shielding film, 24a ... Opening, 25 ... First interlayer insulating film, 26 ... Second interlayer insulating film, 30 ... Color filter, 31 ... Green color filter, 32 ... Blue color filter, 33 ... Red color filter, 40 ... Flattening film, 50 ... Microlens, 51 ... First lens layer, 52 ... Second lens layer, 52a ... Oxygen Supply hole, 6 ... transparent protective film, 70 ... antireflection film, 100 ... camera, 102 ... optical system, 103 ... driving circuit, 104 ... signal processing circuit

Claims (14)

A plurality of light receiving portions formed on the substrate;
A microlens formed in an upper layer of the substrate and corresponding to each light receiving portion;
Covering the microlens, and having a transparent protective film having a lower refractive index than the microlens,
The microlens is
A first lens layer formed of a lens-shaped resin containing refractive index adjusting particles;
An inorganic second lens layer formed so as to cover the first lens layer so as to embed a gap between the adjacent first lens layers , and
Between the substrate and the microlens, a color filter containing a pigment that decomposes by a reduction reaction is disposed,
The second lens layer has an oxygen supply hole formed between the adjacent first lens layers, and oxygen is supplied to the color filter through the oxygen supply hole.
Solid-state imaging device. A plurality of the microlenses are arranged in a matrix,
The oxygen supply hole is provided between the microlenses adjacent in the diagonal direction,
The solid-state imaging device according to claim 1. The refractive index adjusting particles are metal oxide particles.
The solid-state imaging device according to claim 1 or 2. The second lens layer is made of silicon nitride;
The solid-state imaging device according to claim 1. The color filter uses copper phthalocyanine as a pigment,
The solid-state imaging device according to claim 4. The solid-state imaging device according to claim 1, wherein an antireflection film is formed on the transparent protective film or between the microlens and the transparent protective film. The solid-state imaging device according to claim 1, wherein the second lens layer has a film thickness that is equal to or greater than a half of a gap between the adjacent first lens layers. Forming a plurality of light receiving portions on the substrate;
Forming a color filter containing a pigment that decomposes in a reduction reaction on the upper layer of the substrate;
Forming a first lens layer on the upper layer of the substrate on which the color filter is formed using a photosensitive resin containing refractive index adjusting particles;
Exposing and developing the first lens layer to process it into a first lens layer having a pattern corresponding to each light receiving portion;
Forming the first lens layer into a lens shape by heat treatment;
Forming an inorganic second lens layer that covers the first lens layer so as to fill a gap between the adjacent first lens layers;
The second lens layer, have a forming a transparent protective layer having a refractive index lower than the refractive index of the first lens layer and the second lens layer,
After the step of forming the second lens layer and before the step of forming the transparent protective film, oxygen is supplied to the second lens layer in a region between the adjacent first lens layers. Forming holes,
Manufacturing method of solid-state imaging device. Forming the microlens so that a plurality are arranged in a matrix,
Providing the oxygen supply hole between the microlenses adjacent in the diagonal direction;
The manufacturing method of the solid-state imaging device of Claim 8. Forming the second lens layer with silicon nitride;
The manufacturing method of the solid-state imaging device of Claim 8 or 9 . Forming the color filter using copper phthalocyanine as a pigment;
The manufacturing method of the solid-state imaging device of Claim 10. The method further comprises a step of forming an antireflection film after the step of forming the transparent protective film or after the step of forming the second lens layer and before the step of forming the transparent protective film. The manufacturing method of the solid-state imaging device in any one of 8-11. In the step of forming the second lens layer, according to claim 8 which forms the second lens layer having a thickness of 1/2 or more of the gap of said first lens layer adjacent to 12 Manufacturing method of solid-state imaging device. A solid-state imaging device;
An optical system for imaging light on the imaging surface of the solid-state imaging device;
A signal processing circuit that performs predetermined signal processing on an output signal from the solid-state imaging device;
The solid-state imaging device
A plurality of light receiving portions formed on the substrate;
A microlens formed in an upper layer of the substrate and corresponding to each light receiving portion;
Covering the microlens, and having a transparent protective film having a lower refractive index than the microlens,
The microlens is
A first lens layer formed of a lens-shaped resin containing refractive index adjusting particles;
An inorganic second lens layer formed so as to cover the first lens layer so as to embed a gap between the adjacent first lens layers , and
Between the substrate and the microlens, a color filter containing a pigment that decomposes by a reduction reaction is disposed,
The second lens layer has an oxygen supply hole formed between the adjacent first lens layers, and oxygen is supplied to the color filter through the oxygen supply hole.
camera.

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