JP5364989B2 - Solid-state imaging device and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To advance characteristics in sensitivity of a solid-state imaging device, and to improve its characteristics in color mixture. <P>SOLUTION: The device has a plurality of pixels 4, and a waveguide 18 for introducing an incident light L into the photoelectric converter 11 of the pixel. The waveguide 18 is structured with each of color-filter components 8R, 8G, 8B in a color filter 8 as a core, and with a hollow portion 15 formed by a self-alignment between the adjoining color-filter components as a clad portion. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a solid-state imaging device such as a CMOS image sensor or a CCD image sensor, a manufacturing method thereof, and a camera including the solid-state imaging device.

  In recent years, with the miniaturization of pixels and the increase in the number of pixels in a solid-state imaging device, technological development for securing and improving sensitivity characteristics, which are important characteristics of the solid-state imaging device, has been actively performed.

  In a solid-state imaging device used for mobile applications typified by downsizing of a digital still camera and a mobile phone with a camera, the distance from the lens of the camera or camera module to the solid-state imaging device is short. For this reason, the angle of light incident particularly toward the outer periphery of the light receiving region of the solid-state imaging device becomes steep, which deteriorates sensitivity characteristics, luminance shading, and the like, and further causes color mixing. Therefore, establishment of these improvement techniques is desired.

  As a method for improving the sensitivity of a solid-state image pickup device, a back-illuminated CMOS solid-state image pickup device has been developed. In the back-illuminated solid-state imaging device, the area and volume of the photoelectric conversion unit can be formed large, so that the sensitivity characteristics that are important characteristics of the solid-state imaging device can be improved.

  FIG. 22 shows a conventional backside illumination type CMOS image sensor. This CMOS image sensor 120 has a multilayer wiring layer in which a plurality of pixels 123 are two-dimensionally arranged in an imaging region 122 of a silicon semiconductor layer 121 and a multilayer wiring 125 is stacked on the surface side of the semiconductor layer 121 via an interlayer insulating film 124. 126 is formed, and the color filter 128 and the on-chip microlens 129 are formed on the back surface side of the semiconductor layer 121 through the planarization film 127. Further, the instruction board 131 is bonded to the surface of the multilayer wiring layer 126 via the adhesive layer 130.

  The pixel 123 includes, for example, a photodiode (PD) serving as the photoelectric conversion unit 133 and a plurality of pixel transistors. FIG. 22 representatively shows a transfer transistor having a transfer gate electrode 135 among a plurality of pixel transistors. Reference numeral 136 denotes a pixel separation region that separates the pixels 123. The color filter 128 includes a red filter component 128R, a green filter component 128G, and a blue filter component 128B.

  Incidentally, in such a back-illuminated CMOS image sensor 120, the light L incident obliquely on the on-chip microlens 129 may leak into adjacent pixels. For this reason, it does not solve the color mixing problem between adjacent color filter components in the color filter. As a technique for improving color mixing, it is possible to install a known in-layer lens or a light shielding film. However, in the manufacturing process, it is necessary to perform the heat treatment below the heat resistance of the adhesive used when bonding the support substrate and the silicon layer including the wiring layer. There are restrictions on process conditions.

  On the other hand, as another method for improving the sensitivity of a solid-state imaging device in a fine cell (pixel), a waveguide structure using total light reflection represented by an optical cable in a layer has been proposed. For example, in Patent Document 1, an insulating film such as a silicon oxide film (SiO2 film: refractive index n≈1.45) is used for the cladding part, and a silicon nitride film (SiN film: refractive index n≈2.0) is used for the core part. There has been proposed a solid-state image pickup device provided with a waveguide using the. Patent Document 2 also proposes a solid-state imaging device including a waveguide formed by using an air layer for a clad part and a required insulating film for a core part. However, there is a limit to condensing incident light having a large angle on a photodiode that is a photoelectric conversion unit.

  Patent Document 2 also proposes a solid-state imaging device having a structure similar to a waveguide so that each color filter component is surrounded by a bowl-shaped partition having a refractive index smaller than that of the color filter component.

JP 2004-221532 A JP 2006-128433 A

In view of the above-described points, the present invention provides a solid-state imaging device and a method for manufacturing the same, in which the total reflection conditions in the waveguide structure are further improved to improve the sensitivity characteristics and the color mixing characteristics are improved.
Furthermore, this invention provides the camera provided with the said solid-state imaging device.

The solid-state imaging device according to the present invention includes a plurality of pixels and a waveguide that guides incident light to the photoelectric conversion unit of the pixels. The waveguide has a first waveguide portion configured with each color filter component of the color filter as a core portion and a hollow portion formed by a self-aligned line between adjacent color filter components as a cladding portion, the photoelectric conversion portion, A second waveguide section between the color filter and having a first layer as a core section and a hollow section formed outside the first layer as a cladding section, and the second waveguide between parts, supports reflective film on at least the surface is formed is provided between the core portion constituting the second waveguide portion and the support member, constituting the second waveguide section The hollow portion is provided.

  In the solid-state imaging device of the present invention, since the color filter has a total reflection type waveguide function in which the cladding portion is a hollow portion, the light collection efficiency to the photoelectric portion is improved and color mixing is reduced. Since the waveguide has a hollow portion formed of self-aligned lines, light incident on the hollow portion hardly enters the adjacent color filter component, and the spectral characteristics are improved. Thereby, the film thickness of a color filter can be made thin, the distance between a color filter and a photoelectric conversion part can be shortened, and a condensing characteristic improves. If necessary, it is possible to omit the on-chip lens.

  In the method for manufacturing a solid-state imaging device according to the present invention, a sacrificial film is selectively formed only on the side wall of the first color filter component, and another color filter component is formed on the side wall of the first color filter component via the sacrificial film. After forming the sacrificial film, the sacrificial film is removed by etching, and a hollow portion is formed by self-alignment. In this way, the present invention is characterized by the step of forming a color filter having a waveguide function with the hollow portion as a cladding portion and the color filter component as a core portion.

  In the method for manufacturing a solid-state imaging device according to the present invention, after forming a sacrificial film only on the side wall of the first color filter component, another color filter component is formed, the sacrificial film is removed, and a hollow portion is formed between the color filter components. Is forming. That is, since this hollow part is formed by what is called self-aligned, a hollow part with a fine width can be formed. The hollow portion and the color filter component constitute a waveguide, and a color filter having a total reflection type waveguide function is formed.

The camera according to the present invention includes a solid-state imaging device, an optical lens system, and signal processing means. This solid-state imaging device has a plurality of pixels and a waveguide that guides incident light to the photoelectric conversion unit of the pixel, and the waveguide uses each color filter component of the color filter as a core portion, and between adjacent color filter components. Between the first waveguide part configured as a cladding part with a hollow part formed of self-aligned lines, the photoelectric conversion part and the color filter, the first layer as a core part, and the first layer A second waveguide portion configured as a clad portion with a hollow portion formed on the outer side, and a support having at least a reflective film formed on the surface is provided between the second waveguide portions . The hollow portion constituting the second waveguide portion is provided between the core portion constituting the two waveguide portions and the support.

With the solid-state imaging device according to the present invention, it is possible to improve sensitivity characteristics and improve color mixing characteristics.
According to the method for manufacturing a solid-state imaging device according to the present invention, it is possible to manufacture a solid-state imaging device with improved sensitivity characteristics and improved color mixing characteristics.
The camera according to the present invention can provide a highly reliable camera with improved sensitivity characteristics and improved color mixing characteristics.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a first embodiment of a solid-state imaging device according to the present invention. The solid-state imaging device according to the present embodiment is applied to a backside illumination type CMOS image sensor. In the solid-state imaging device 1 according to the present embodiment, a plurality of pixels 4 are two-dimensionally arranged in an imaging region 3 of a semiconductor layer (for example, a silicon layer) 2, and a multilayer is formed on the surface side of the semiconductor layer 2 via an interlayer insulating film 5. A multilayer wiring layer 7 in which the wirings 6 are laminated is formed, and a color filter 8 having a waveguide structure is disposed on the back side of the semiconductor layer 2. Further, a support substrate 10 made of, for example, a silicon substrate is bonded to the surface of the multilayer wiring layer 7 via an adhesive layer 9.

  The pixel 4 is composed of, for example, a photodiode (PD) serving as the photoelectric conversion unit 11 and a pixel transistor including a plurality of MOS transistors. The pixel transistor can be constituted by four transistors, for example, a transfer transistor, a reset transistor, an amplification transistor, and a selection transistor. Alternatively, the pixel transistor can be composed of three transistors: a transfer transistor, a reset transistor, and an amplification transistor. The pixel transistor can also be configured with other numbers of transistors. In FIG. 1, a transfer transistor having a transfer gate electrode 13 among a plurality of pixel transistors is shown as a representative. Reference numeral 19 denotes a pixel separation region that separates adjacent pixels.

  In the present embodiment, the color filter 8 has a waveguide function. That is, a hollow portion formed by self-alignment at the boundary between the first color, for example, the green (G) filter component 8G, the second color, for example, the red (R) filter component 8R, and the third color, for example, the blue (B) filter component 8B. 15 is formed. Here, the refractive index of the hollow portion 15 is 1.0, for example, in the case of air, and the refractive indexes of the color filter components 8G, 8R, 8B are about 1.6 to 1.7. Note that the hollow portion 15 has a refractive index close to 1.0 even when it is filled with a reaction gas or the like when forming a capping film 17 to be described later, instead of air.

  Accordingly, in each of the color filter components 8G, 8R, and 8B, a total reflection type waveguide 18 is formed in which the filter components 8G, 8R, and 8B are the core portions and the outer peripheral hollow portion 15 is the cladding portion. As will be described later, the hollow portion 15 is formed of self-aligned lines, and thus has a width d1 of 150 nm or less, that is, a fine width of about 150 nm to 10 nm.

  The color filter 8 is formed on the back surface of the semiconductor layer 2 via a flat film 16 made of an insulating film or a passivation film. On the surface of the color filter 8, a hollow portion cap film 17 that seals the hollow portion 15 is formed. "

  The cap layer 17 may be omitted for reasons such as process simplification. For example, when a microlens or the like is installed on the color filter 8, the cap layer 17 is necessary because an organic film may enter the hollow portion 15 and cause defects. However, the cap layer 17 is not necessarily required when a microlens or the like is not installed.

An example of the color filter 8 is shown in FIG. The color filter 8 is a so-called Bayer array color filter. In the Bayer array, a green-red column in which green (G) filter components 8G and red (R) filter components 8R are alternately arranged in the horizontal direction, and a green (G) filter component 8G and a blue (B) filter in the horizontal direction. Blue-red columns in which the components 8B are alternately arranged are alternately arranged in the vertical direction.
In the color filter 8 of FIG. 1, filter components 8R, 8G, and 8B of red (R), green (G), and blue (B) are arranged in the horizontal direction for convenience of explanation.

  As shown in FIG. 1, the solid-state imaging device 1 according to the first embodiment is completed by omitting the on-chip microlens on the color filter 8.

Next, a method for manufacturing the above-described solid-state imaging device 1, particularly a method for manufacturing the color filter 8 having a waveguide structure, will be described with reference to FIGS.
First, as shown in FIG. 3A, a flat film 16 made of an insulating film or a passivation film is formed on the back surface side of the semiconductor layer 2 on which the plurality of pixels 4 including the photoelectric conversion unit 11 and the pixel transistors are formed. The flat film 16 can be formed of a plasma nitride film, a high-density plasma oxide film (HDP-SiO 2 film), or the like.

  Next, as shown in FIG. 3B, for example, a green filter material layer 8G ′ of the first color is formed on the entire surface of the flat film 16.

  Next, a photoresist layer is formed on the green filter material layer 8G ′, exposed and developed through an optical mask, and as shown in FIG. 3C, positions corresponding to green pixels on the green filter material layer 8G ′. Next, a resist mask 18 is formed.

  Next, as shown in FIG. 4D, the green filter material layer 8G ′ is selectively removed by a dry etching method using the resist mask 18 as an etching resistant mask, and a green filter component 8G is formed at a position corresponding to a green (G) pixel. Form. After the dry etching, the resist mask 18 that is no longer needed is peeled off using an organic solvent or the like. As a patterning method for the green filter component 8G, since the generally used color filter itself is a photosensitive photoresist, the photosensitive green filter material layer (photoresist layer) is used as it is. It can also be formed by a known photoresist method in which exposure and development are performed through an optical mask.

  Next, as shown in FIG. 4E, a thin sacrificial film 19 is formed on the entire surface including the surface of the green filter component 8G. The sacrificial film 19 is a plasma silicon nitride film (P-SiN film) in this example. This sacrificial film 19 is for forming a hollow portion of a waveguide structure in the present invention described later. As the sacrificial film 19, a material film having an etching rate different from that of the color filter component, such as an amorphous silicon film or a polycrystalline silicon film, can be used. The thickness d1 of the sacrificial film 19 is set to 150 nm or less, and in this example, 80 nm. The film-forming temperature of the sacrificial film 19 is set to be equal to or lower than the heat resistance temperature of the adhesive layer 9 (see FIG. 1) and the color filter component, in this example, the green filter component 8G. . The lower limit is about 80 ° C. G, which is lower than 80 ° C., hinders film formation.

  Next, as shown in FIG. 4F, the sacrificial film 19 is etched back by using an anisotropic dry etching method, leaving only the peripheral side wall of the green filter component 8G and removing everything else.

  Next, as shown in FIG. 4G, in the same manner as the green filter component 8G, the red (R) pixel is adjacent to one side of the green filter component 8G via the sacrificial film 19. The red filter component 8R is formed so as to correspond. Here, as the patterning method of the red filter component 8R, as described in the patterning method of the green filter component 8G, a method of patterning by dry etching through a photoresist mask, as well as a photosensitive red filter, are used. A known photoresist method using a material layer (photoresist layer) can also be used.

  Next, as shown in FIG. 5H, in the same manner as the green filter component 8G, the blue (B) pixel is adjacent to the other side of the green filter component 8G via the sacrificial film 19. The blue filter component 8B is formed so as to correspond. Here, as the blue filter component 8B patterning method, as described in the above-described patterning method of the green filter component 8G, in addition to a method of patterning by dry etching through a photoresist mask, a photosensitive blue filter material is used. A known photoresist method using a layer (photoresist layer) can also be used.

  Next, as shown in FIG. 5I, the sacrificial film 19 is selectively removed by dry etching using an isotropic dry etching method, and a hollow portion 15 is formed between the adjacent color filter components 8G, 8R, and 8B. Form. For example, chemical dry etching can be used as the isotropic dry etching. The hollow portion 15 is formed of self-alignment as is apparent from the above-described process. Therefore, the hollow portion 15 can be formed with a fine width of 150 nm or less.

  Next, as shown in FIG. 5J, a capping film 17 for sealing the hollow portion 15 is formed on the color filter in which the hollow portion 15 is formed. As the capping film 17, a plasma / silicon nitride film, a plasma / silicon oxide film, or the like can be used. In this example, a plasma silicon oxide film is used.

  In this way, the back-illuminated solid-state imaging device 1 having the function of the color filter 8 having the waveguide structure of the target first embodiment and having no on-chip microlens is obtained.

  According to the solid-state imaging device 1 according to the first embodiment, the color filter 8 having the total reflection type waveguide structure 18 is configured with the hollow portion 15 as a cladding portion and the color filter components 8G, 8R, and 8B as core portions. As a result, as shown in FIG. 1, the light L incident on each color filter component 8G, 8R, 8B of the color filter is totally reflected at the boundary surface between the hollow portion 15 and the color filter component, and photoelectric conversion of each color pixel is performed. Incident on the part 11. Therefore, even if the on-chip microlens is omitted, it is possible to provide a solid-state imaging device that reduces color mixing, improves sensitivity, and further improves sensitivity shading.

  In the present embodiment, since the hollow portion 15 is formed by self-alignment, the hollow portion 15 having a fine width of 150 nm or less is formed, and a solid-state imaging device having excellent spectral characteristics can be configured. In addition, since the spectral characteristics are excellent, the thickness of the color filter 8 can be reduced, the distance between the color filter 8 and the photoelectric conversion unit 11 can be shortened, and the light collection characteristics can be improved.

  Incidentally, when forming the groove in the hollow portion using the lithography technique, for example, even if KrF excimer laser light is used, the limit is about 180 nm, and a groove width smaller than that is not obtained. When the width of the hollow portion is widened, the light incident on the hollow portion at the color filter component boundary easily enters the adjacent color filter component, and the spectral characteristics deteriorate. When the film thickness of the color filter is increased in order to improve the deterioration of the spectral characteristics, the distance between the color filter and the photoelectric conversion unit is increased and the light condensing characteristic is deteriorated.

  Furthermore, in the present embodiment, since a known on-chip lens can be omitted, the number of manufacturing steps can be reduced, manufacturing can be simplified, and manufacturing cost can be reduced.

In the above example, the present invention is applied to the back-illuminated CMOS image sensor. However, the present invention is not limited to this, but can be applied to a front-illuminated CMOS image sensor. The present invention can also be applied to a CCD image sensor as will be described later.
In the above example, the on-chip microlens 8 on the color filter 8 is omitted, but an on-chip microlens may be formed on the color filter. When an on-chip microlens is provided, the light collection efficiency can be further improved.

  FIG. 6 shows a second embodiment of the solid-state imaging device according to the present invention. The solid-state imaging device according to the present embodiment is applied to a CCD image sensor. In addition to the color filter having the waveguide function described above, a hollow portion is also formed in the region between the color filter and the photoelectric conversion portion as a cladding portion. It is configured by forming a waveguide.

  That is, in the solid-state imaging device 21 according to the second embodiment, a plurality of photoelectric conversion units 23, for example, photodiodes are regularly arranged in a two-dimensional manner in an imaging region of a semiconductor substrate (for example, a silicon substrate) 22. A vertical transfer register 24 having a CCD structure is formed for each photoelectric conversion unit row. Although not shown, a horizontal transfer register having a CCD structure is formed at the end of each vertical transfer register 24, and an output unit is connected to a floating diffusion unit at the final stage of the horizontal transfer register.

  On the imaging region, a total reflection type second layer having a hollow portion 28 as a cladding portion and a first layer 29, for example, an insulating film as a core portion, in an area corresponding to each pixel via an intralayer lens 25. A waveguide 27 is formed. Further, the color filter 8 having the total reflection type first waveguide 18 having the hollow portion 15 similar to the above as a cladding portion and the color filter components 8R, 8G, and 8B as core portions is formed thereon.

  The semiconductor substrate 22 is a first conductivity type, in this example, an n-type silicon substrate, and an overflow barrier region 31 composed of a second conductivity type p-type semiconductor region is formed on the substrate 22. A p-type semiconductor well region 32 is formed. The photodiode that becomes the photoelectric conversion unit 23 is formed in the p-type semiconductor well region 32.

  On the other hand, the vertical transfer register 24 is formed by an n-type buried channel region 33 formed in the p-type semiconductor well region 32, a gate insulating film 34 thereon, and a transfer electrode 35 formed on the gate insulating film 34. The Between the photoelectric conversion unit 23 and the vertical transfer register 24, a charge reading unit 36 in which a transfer gate electrode 35 is partially extended is formed. Reference numeral 40 denotes a channel stop region that separates adjacent pixels provided on the opposite side of the charge reading unit 36 of the photoelectric conversion unit 23. A light shielding layer 37 is formed on the entire surface of each photoelectric conversion unit 23 except the light receiving region 38 (see FIG. 7) so as to cover the transfer gate electrode 35 with an insulating film 39 interposed therebetween.

  The in-layer lens 25 is formed by an insulating film 41 having a first refractive index, such as a reflow film such as boron phosphorus glass (BPSG), and an insulating film 42 having a second refractive index thereon, such as a plasma silicon nitride film. Consists of a convex lens.

  The second waveguide 27 is formed on the planarized surface of the insulating film 42 of the second refractive index made of, for example, a plasma silicon nitride film. The second waveguide 27 has a hollow portion 28, for example, air (refractive index n is 1.0) as a cladding portion, and an insulating film, for example, a silicon oxide film (refractive index) that becomes the first layer 29 having a higher refractive index than air. n is about 1.45), or a silicon nitride film (refractive index n is about 2.0) is used as the core portion.

  In this example, a support member whose side wall is inclined, for example, a support body 43 having a triangular cross section, is formed on the insulating film 42 corresponding to the light shielding film 37 so as to surround the photoelectric conversion unit 23. The region surrounded by the support 43 is formed on an inclined surface whose width becomes narrower toward the insulating film 42 side. On the other hand, a first layer 29 serving as a core portion is formed on the insulating film 42 so as to correspond to the photoelectric conversion portion 23, and a support inclined surface is formed between the first layer 29 and the support 43. A hollow portion 28 is formed as a clad portion extending in parallel. The first layer 29 and the hollow portion 28 constitute a total reflection type second waveguide 27. The hollow portion 28 may be filled with air, or may be filled with a reaction gas at the time of subsequent film formation.

  A cap film 45 is formed on the second waveguide 27 so as to seal the hollow portion 28, and a planarization film 46 is further formed thereon. The cap film 45 is uniformly formed over the entire upper surface of the first layer 29 together with the opening of the hollow portion 28 in order to prevent the organic film such as the color filter 8 from permeating. The cap film 45 can be formed of a required insulating film, for example, a nitride film such as a silicon oxide film or a silicon oxynitride film that functions as an antireflection film in this example. The material of the cap film 45 is preferably an inorganic film, and more preferably an inorganic film that also serves to prevent reflection of the surface of the high refractive index material. Note that after the cap film 45 is formed, the antireflection film may be formed again, or the antireflection film is not necessarily formed.

  Then, the color filter 8 having the first waveguide 18 having the hollow portion 15 at the boundary between the adjacent color filter components 8R, 8G, and 8B described in FIG. 1 is formed on the planarizing film 46. Further, a cap film 17 is formed thereon. In this way, the solid-state imaging device 21 of the second embodiment is configured.

  Next, a manufacturing method of the solid-state imaging device 21 according to the above-described second embodiment will be described with reference to FIGS. 7 to 11 and FIGS. 3 to 5.

7 to 11 show manufacturing steps up to the formation of the second waveguide 27 before the color filter 8 is formed.
First, as shown in FIG. 7A, a p-type overflow barrier region 31 and a p-type semiconductor well region 32 are formed in an n-type silicon semiconductor substrate 21, and the n-type semiconductor region and p + accumulation are formed in the p-type semiconductor well region 32. A photodiode 23 composed of layers and an n-type buried channel layer 33 are formed. Although not shown in detail, a channel stop region 40 and a charge readout region 36 are formed. Next, a transfer electrode 35 made of, for example, polycrystalline silicon having a two-layer film structure is formed on the surface of the semiconductor substrate via a gate insulating film 34, and a light shielding layer 37 is formed via an interlayer insulating film 39. Further, for example, a plasma / silicon nitride film 42 is deposited on the reflow film 41 made of, for example, boron / phosphorus glass, and the inner lens 25 is formed on the light receiving region 38.

  Next, as shown in FIG. 7B, a layer 43 </ b> A serving as a support is formed on the planarized upper surface of the plasma silicon nitride film 24. For the layer 43A serving as the support, aluminum, silver, gold, copper, tungsten, a silicon nitride film, a polycrystalline silicon film, a silicon oxide film, or the like can be used. In this example, aluminum 43 is formed by sputtering to form a layer 43A to be a support.

  Next, as shown in FIG. 7C, a resist mask 52 patterned to a required width is formed using a lithography technique and an etching technique at a position corresponding to the light shielding layer 37 on the layer 43A to be a support.

  Next, as shown in FIG. 8D, the layer 43A serving as the support is selectively removed by dry etching, for example, via the resist mask 52, so that the cross section is substantially triangular (that is, the top is partially flat). A support body 43 having a certain triangular shape is formed. The support 43 is formed on the light shielding layer 37 so as to surround the light receiving region 38. Here, the support body 43 is processed into a forward tapered shape, that is, a substantially triangular shape, but may be processed substantially vertically as shown in the following embodiments.

Next, as shown in FIG. 8E, the resist mask 52 that is no longer necessary after dry etching is removed, and then a sacrificial film 54 having a required film thickness is formed on the entire surface of the support 43 and the surface of the plasma silicon nitride film 42. Is deposited. The sacrificial film 54 is used to make the clad portion constituting the waveguide later hollow. Then, using a lithography technique and an etching technique, that is, a photoresist film is formed on the entire surface, and the photoresist film on the upper part of the light receiving region 38 is selectively removed so as to correspond to the support body 43 having a substantially triangular cross section. A resist mask 55 is formed on the film 54.
For the sacrificial film 54, amorphous silicon, polycrystalline silicon, or the like is used. Further, when aluminum, silver, gold, copper, or a polycrystalline silicon film is used as the support 43, a silicon oxide film or a silicon nitride film may be formed after the support 43 is processed. In particular, when a polycrystalline silicon film is used for the support 43, the silicon oxide film and the silicon nitride film function as an etching stopper for dry etching at the time of core material opening processing which will be performed later.

  Next, as shown in FIG. 8F, only the sacrificial film 53 on the support 43 is left, and the other part of the sacrificial film 53 is selectively removed by dry etching through the resist mask 55.

  Next, as shown in FIG. 9G, a first layer 56 to be the core portion of the waveguide is formed on the entire upper surface. The material of the first layer 56 may be any material that has a refractive index larger than the refractive index (n = 1) of the hollow portion that basically becomes the cladding portion, for example, the air layer. Here, the refractive index ratio of the known silicon oxide film (refractive index n≈1.45) to the silicon nitride film (refractive index n≈2.0) = 1.45 / 2.0 = 0.725. Larger material combinations are desirable.

  An explanation of the critical angle in total reflection is shown in FIG. In addition, the critical angle of the waveguide by a known combination of a silicon oxide film and a silicon nitride film is 46.5 °. On the other hand, when air (refractive index n = 1) is used for the cladding, FIG. 13 shows the change in the critical angle when the refractive index of the material is changed.

  FIG. 13 shows a state in which the incident light L is incident on the boundary surface 100 between the material having the refractive index (NI) and the material having the refractive index (NII) at the incident angle θ and reflected by the boundary surface 100. Total reflection is a phenomenon in which, when light travels from a material having a large refractive index (NI) to a material having a small refractive index (NII), the incident light L does not pass through the boundary surface 100 and is totally reflected. When the incident angle θ is equal to or larger than a certain angle, total reflection is performed, and this angle is called a critical angle. The critical angle θ can be expressed by Equation 1.

屈折率差が大きい程、臨界角θは小さくなり、全反射角領域（図中Ａ）が広がる。

The larger the refractive index difference, the smaller the critical angle θ and the wider the total reflection angle region (A in the figure).

  As can be seen from FIG. 13, by setting the refractive index of the core part material to 1.4 or more, the critical angle in the known combination structure is reduced, and the total reflection characteristics are improved.

  As this core material, silicon oxide film, silicon nitride film, silicon oxynitride film, boron phosphorus glass, niobium oxide film, titanium oxide film, polyimide resin, polymethyl methacrylate, allyl diglycol carbonate, diallyl phthalate, Polycarbonate, polybenzyl methacrylate, polyphenyl methacrylate, polydiallyl phthalate, polystyrene, poly-p-promophenyl methacrylate, polypentachlorophenyl methacrylate, poly-o-chlorostyrene, poly-α-naphthyl methacrylate, polyvinyl naphthalene, polyvinyl carbazole, poly For example, pentabromophenyl methacrylate, a polymer resin in which metal fine particles of zinc oxide, zirconium oxide, titanium oxide, tin oxide and the like are dispersedly contained are used.

Hereinafter, a process flow in the case where a silicon nitride film is applied to the core material will be described. That is, in FIG. 9G, in this example, a silicon nitride film is used for the first layer 29 serving as the core portion.
Next, as shown in FIG. 9H, a photoresist film 57 is applied on the first layer 56 of silicon nitride so as to be substantially flat.

  Next, as shown in FIG. 9I, the photoresist film 57 and the first layer (silicon nitride film) 56 formed in a convex shape are simultaneously etched back using a dry etching method. At this time, since it is desirable to process the surface of the first layer (silicon nitride film) 56 substantially flatly, it is desirable that the etching speed in dry etching is approximately the same for the silicon nitride film and the photoresist film. . As a planarization method, a CMP method (Chemical Mechanical Polish) or the like can also be used. Further, planarization by a combination of an etching method and a CMP method may be performed.

  Next, as shown in FIG. 10J, a resist mask 58 having an opening 59 corresponding to the top of the support 43 is formed on the first layer (silicon nitride film) 56.

  Next, as shown in FIG. 10K, the first layer (silicon nitride film) 56 is selectively patterned by dry etching through the resist mask 58, and the first layer (silicon silicon) corresponding to the top of the support 43 is formed. An opening 60 that leads to the sacrificial film 53 is formed in the nitride film 56. Thereafter, the resist mask 58 is removed.

  Next, as shown in FIG. 10L, the sacrificial film 53 is removed through the opening 60 by isotropic dry etching. By removing the sacrificial film 53, a hollow layer (for example, an air layer) 28 parallel to the inclined surface is formed along the inclined surface of the support 43. A second waveguide 27 is formed by the hollow portion 28 and the first layer 29.

  Next, as shown in FIG. 11M, the sealing layer 45 for sealing (filling in) the opening 60 of the first layer (silicon nitride film) 29 is formed in the opening 60 and the first layer (silicon nitride film). ) 29 over the entire surface. The sealing layer 45 is formed by a dry film forming method. The reason for filling the hole by the dry film forming method is to prevent the sacrificial film 53 from being infiltrated into the region removed by dry etching when the solution-like organic planarizing film to be subsequently applied is applied. The dry film forming method is not particularly limited, and examples thereof include a CVD method (Chemical Vapor Deposition), a sputtering method, a vapor deposition method, and an ion plating method. Here, a silicon nitride film is embedded in the opening 60 as the sealing layer 45 using a P-CVD method (Plasma Chemical Vapor Deposition).

  Next, as shown in FIG. 11N, a planarizing film 46 made of, for example, an acrylic resin is formed on the sealing layer 45 made of a silicon nitride film formed by the P-CVD method.

  After the second waveguide 27 is formed and the sealing layer 45 and the planarizing film 46 are formed, the first waveguide is formed on the planarizing film 46 by using the same process as the process of FIGS. 4C to 6J described above. The color filter 8 having the waveguide 18 is formed to obtain the target solid-state imaging device 21 of the second embodiment.

  According to the solid-state imaging device 21 according to the second embodiment described above, the incident light L is guided to each pixel side by the color filter 8 having the total reflection type first waveguide function, and further the total reflection type second guide. Since the light is guided to the photoelectric conversion unit 23 of each pixel through the waveguide 27, in the CCD image sensor, the light collection efficiency can be improved and the sensitivity characteristic can be further improved. In addition, the luminance seeding characteristic and the color mixing characteristic can be improved.

  In the present embodiment, as described above, since the hollow portion 15 constituting the first waveguide 18 is formed by self-alignment, the hollow portion 15 having a fine width of 150 nm or less is formed, and the solid-state imaging excellent in spectral characteristics A device can be configured. In addition, since the spectral characteristics are excellent, the thickness of the color filter 8 can be reduced, the distance between the color filter 8 and the photoelectric conversion unit 11 can be shortened, and the light collection characteristics can be improved.

  A cap film 45 that seals the opening of the hollow portion 28 that constitutes the second waveguide 27 is formed on the entire surface. When the cap film 45 has a function as an antireflection film, the incident light L is further condensed. Efficiency can be improved. Since the on-chip microlens is omitted, the number of manufacturing steps can be reduced correspondingly, and the cost can be reduced.

  The configuration of the second waveguide 27 can take various configurations. 14 to 19 show modified examples of the second waveguide 27. 14 to 19 show a configuration of a solid-state imaging device including a normal color filter and a second waveguide 27, that is, a CCD image sensor.

  The solid-state imaging device 71 of FIG. 14 includes a waveguide 27 having the same configuration as described above, and a normal color filter 65 is formed via a sealing film 45 and a planarizing film 46, and an on-chip microlens is further formed thereon. 66 is formed. Since the configuration of the lower side of the waveguide 27 is the same as that in FIG. 7, the same reference numerals are given to the portions corresponding to those in FIG.

  In the solid-state imaging device 72 of FIG. 15, a reflective film 67 is formed in parallel with the hollow layer 28 on the surface of the support 43 opposite to the first layer 29 of the hollow layer 28 of the waveguide 27 in this example. Configured. As the reflective layer 67, for example, a metal reflective film such as aluminum, silver, gold, or copper can be used. Since other configurations are the same as those in FIG. 14, parts corresponding to those in FIG.

  According to the solid-state imaging device 72, the reflection layer 67 is formed on the surface of the support 43 in contact with the hollow layer 28 of the waveguide 27. Therefore, the light leaked from the waveguide 27 is partially reflected without being totally reflected. The light is reflected by the layer 67 and enters the light receiving region 20. Therefore, the loss of so-called total reflection light can be compensated by the reflection layer 67, so that higher sensitivity can be achieved.

  In the solid-state imaging device 73 of FIG. 16, the support body 43 at a position corresponding to the light shielding film 37 is formed in a quadrangular cross section whose wall surface is a substantially vertical surface. The waveguide 27 is constituted by a hollow layer 28 and a first layer 29 along a substantially vertical wall surface of the support 43. Although not shown, the reflective layer 67 shown in FIG. 15 can be formed on the surface of the support 43. Since other configurations are the same as those in FIG. 14, parts corresponding to those in FIG.

The solid-state imaging device 74 of FIG. 17 is configured by forming a light shielding and supporting body 68 in which the light shielding film 37 and the supporting body 43 are integrally formed. The light shielding and supporting body 68 is desirably formed of a metal film that can be used as a reflective film such as aluminum, silver, gold, or copper. Since other configurations are the same as those in FIG. 14, parts corresponding to those in FIG.
In the solid-state imaging device 74, since the light shielding / supporting body 68 in which the light shielding layer and the support are integrated is formed, the number of components can be reduced.

In the solid-state imaging device 75 of FIG. 18, the waveguide 77 is formed to include a first layer 78 serving as a core portion and a second layer 79 serving as a cladding portion, and the first layer of the second layer 79 is further formed. The reflection layer 80 is formed on the surface opposite to the surface 78, that is, the surface of the support 43. The first layer 78 serving as the central core portion can be formed of a material having a high refractive index, for example, a silicon nitride film. The second layer 79 serving as the outer cladding portion can be formed of a material having a low refractive index, such as a silicon oxide film, porous silica, or a fluorine-based resin. Porous silica is preferable because it has a lower refractive index than that of a silicon oxide film or the like because air exists in the pores. That is, when the waveguide 77 is formed using porous silica, the difference in refractive index between the core portion and the tuck portion can be increased, and the total reflection condition can be improved.
Other configurations including the reflective layer and the support material are the same as those in FIGS. 15 and 16, and therefore, the same reference numerals are given to the portions corresponding to FIGS. .
Since the solid-state imaging device 75 has a configuration including the reflection layer 80 in addition to the total reflection type waveguide 77, the loss of the total reflection light is compensated by the reflection layer 80, and the light collection efficiency is improved. A highly sensitive solid-state imaging device can be obtained.

  The solid-state imaging device 76 of FIG. 19 forms the first layer 29 at a position corresponding to the photoelectric conversion unit 23, and forms the second layer 82 made of an interlayer insulating film so as to surround the first layer 29. A hollow portion 28 is formed between the first and second layers 29 and 82, and the waveguide 27 is formed by the hollow portion 28 and the first layer 29. Since other configurations are the same as those in FIG. 14, parts corresponding to those in FIG.

  In the embodiment of the present invention, as shown in FIG. 6, the waveguides 27 and 77 shown in FIGS. 15 to 19 are used as the second waveguide, and the second waveguides 27 and 77, A solid-state imaging device can also be configured by combining the color filter 8 having one waveguide 18.

  FIG. 20 shows a third embodiment of the solid-state imaging device according to the present invention. The solid-state imaging device according to the present embodiment is applied to a CCD image sensor. In the solid-state imaging device 84 according to the present embodiment, a plurality of photoelectric conversion units 23, for example, photodiodes are regularly arranged in a two-dimensional manner in the imaging region of the semiconductor substrate 22, as described with reference to FIG. Thus, a vertical transfer register 24 having a CCD structure is formed for each photoelectric conversion unit row. Although not shown, a horizontal transfer register having a CCD structure is formed at the end of each vertical transfer register 24, and an output unit is connected to a floating diffusion unit at the final stage of the horizontal transfer register.

  In the semiconductor substrate 22, an overflow barrier region 31 and a semiconductor well region 32 are formed, and the photoelectric conversion unit 23 is formed in the semiconductor well region 32. The vertical transfer register 24 is formed by an n-type buried channel region 33 formed in the semiconductor well region 32, a gate insulating film 34 thereon, and a transfer electrode 35 formed on the gate insulating film 34. Between the photoelectric conversion unit 23 and the vertical transfer register 24, a charge reading unit 36 in which a transfer gate electrode 35 is partially extended is formed. A light shielding layer 37 is formed on the entire surface excluding the light receiving region of each photoelectric conversion unit 23 so as to cover the transfer gate electrode 35 with an insulating film 39 interposed therebetween.

  In the present embodiment, the color filter 8 in which the waveguide 18 is formed with the boundary portion between the color filter components 8R, 8G, and 8B described above as the hollow portion 15 is formed on the planarizing film 85. .

  According to the solid-state imaging device according to the third embodiment, as described above, the incident light L is guided to the photoelectric conversion unit 23 of each pixel by the color filter 8 having a total reflection type waveguide function. In the image sensor, the light collection efficiency is improved, and the sensitivity characteristics can be further improved. In addition, the luminance seeding characteristic and the color mixing characteristic can be improved. Furthermore, since the hollow portion 15 constituting the waveguide 18 is formed with a fine width by self-alignment, a solid-state imaging device having excellent spectral characteristics can be configured. In addition, since the spectral characteristics are excellent, it is possible to reduce the film thickness of the color filter 8, the distance between the color filter and the photoelectric conversion unit 11 is shortened, and the light collection characteristics can be improved. Since the on-chip microlens is omitted, the number of manufacturing steps can be reduced correspondingly, and the cost can be reduced.

  In the configuration of FIG. 20, an on-chip microlens may be further formed on the color filter 8.

  As described above, the solid-state imaging device according to the present embodiment includes the color filter 8 that has the cladding portion of the hollow portion 15 with a fine width and has a total reflection type waveguide function, thereby providing sensitivity characteristics. Further, it is possible to improve color mixing characteristics, luminance shading characteristics, and spectral characteristics.

The solid-state imaging device according to the embodiment of the present invention is suitable for application to mobile applications represented by small digital cameras and camera-equipped mobile phones.
The present invention can constitute a camera (including a camera module) incorporating the solid-state imaging device of the above-described embodiment. FIG. 21 shows an embodiment of a camera according to the present invention. The imaging camera 110 according to the present embodiment includes a solid-state imaging device 111, an optical lens system 112, an input / output unit 113, a signal processing device (Digital Signal Processors) 114, and an optical lens system control device according to any of the embodiments described above. A central processing unit (CPU) 115 can be incorporated into one unit. As a camera, it can also be comprised only with the solid-state imaging device 111, the optical system 112, and the input-output part 113. FIG. A camera including the solid-state imaging device 111, the optical lens system 112, the input / output unit 113, and the signal processing device 114 can also be configured.

  With the camera according to the present embodiment, the sensitivity can be improved. In addition, luminance shading caused by a difference in incident angle within the imaging surface and optical color mixing to adjacent pixels can be reduced.

It is a block diagram of the principal part which shows 1st Embodiment of the solid-state imaging device concerning this invention. It is a top view which shows the example of a color filter. 8A to 8C are manufacturing process diagrams (part 1) of the solid-state imaging device according to the first embodiment. DG is a manufacturing process diagram (No. 2) of the solid-state imaging device according to the first embodiment; H to J are manufacturing process diagrams (part 3) of the solid-state imaging device according to the first embodiment. It is a block diagram of the principal part which shows 2nd Embodiment of the solid-state imaging device which concerns on this invention. FIGS. 8A to 8C are manufacturing process diagrams (part 1) of a solid-state imaging device according to a second embodiment. FIGS. DF is a manufacturing process diagram (part 2) of the solid-state imaging device according to the second embodiment; It is a manufacturing process figure (the 3) of the solid-state image sensor which concerns on GI 2nd Embodiment. J to L are manufacturing process diagrams (part 4) of the solid-state imaging device according to the second embodiment. MN is a manufacturing process diagram (part 5) for a solid-state imaging device according to the second embodiment; It is explanatory drawing with which it uses for description of a total reflection and a critical angle. It is a graph which shows the relationship between a core part refractive index at the time of using a hollow part for a clad part, and a critical angle. It is a block diagram which shows the example of a solid-state imaging device provided with the waveguide applied to the 1st waveguide of 2nd Embodiment. It is a block diagram which shows the other example of the solid-state imaging device provided with the waveguide applied to the 1st waveguide of 2nd Embodiment. It is a block diagram which shows the other example of the solid-state imaging device provided with the waveguide applied to the 1st waveguide of 2nd Embodiment. It is a block diagram which shows the other example of the solid-state imaging device provided with the waveguide applied to the 1st waveguide of 2nd Embodiment. A and B are a configuration diagram illustrating another example of a solid-state imaging device including a waveguide applied to the first waveguide according to the second embodiment, and an enlarged view of a main part thereof. It is a block diagram which shows the other example of the solid-state imaging device provided with the waveguide applied to the 1st waveguide of 2nd Embodiment. It is a block diagram of the principal part which shows 3rd Embodiment of the solid-state imaging device which concerns on this invention. It is a block diagram which shows embodiment of the camera which concerns on this invention. It is a block diagram of the principal part which shows the example of the conventional back irradiation type cmos image sensor.

Explanation of symbols

  1 .... Solid-state imaging device 2 .... Semiconductor layer 3 .... Image area 4 .... Pixel 5 .... Interlayer insulation film 6 .... Wiring layer 7, ... Multi-layer wiring layer 8, ... Color filter 8R, 8G, 8B ... Color filter component, 9 ... Adhesive layer, 10 ... Support substrate, 11 ... Photoelectric conversion part, 13 ... Transfer gate electrode, 15 ... Hollow part, 18 ... Waveguide , 19 ·· Pixel separation region, 27 · · Waveguide, 28 · · Hollow portion, 29 · · First layer

Claims (5)

A plurality of pixels;
A waveguide for guiding incident light to the photoelectric conversion portion of the pixel;
The waveguide is
Each color filter component of the color filter as a core part, a first waveguide part configured as a cladding part a hollow part formed by self line between adjacent color filter components;
A second waveguide section between the photoelectric conversion section and the color filter, wherein the first layer is a core section and the hollow section formed outside the first layer is a cladding section. ,
Between the second waveguide portions, a support having at least a reflective film formed on the surface is provided,
The solid-state imaging device, wherein the hollow portion constituting the second waveguide portion is provided between the core portion constituting the second waveguide portion and the support. The solid-state imaging device according to claim 1, wherein the support is made of a reflective film. The solid-state imaging device according to claim 1, wherein the support has an inclined surface whose width is narrowed toward the first waveguide portion. The solid-state imaging device according to any one of claims 1 to 3, the on-chip microlens is formed on the color filter. A solid-state imaging device, an optical lens system, and signal processing means;
The solid-state imaging device
A plurality of pixels;
A waveguide for guiding incident light to the photoelectric conversion portion of the pixel;
The waveguide is
Each color filter component of the color filter as a core part, a first waveguide part configured as a cladding part a hollow part formed by self line between adjacent color filter components;
A second waveguide section between the photoelectric conversion section and the color filter, wherein the first layer is a core section and the hollow section formed outside the first layer is a cladding section. ,
Between the second waveguide portions, a support having at least a reflective film formed on the surface is provided,
The camera in which the hollow portion constituting the second waveguide portion is provided between the core portion constituting the second waveguide portion and the support.

Images